The less files should be compiled once and then cached for use unless you have the "Automatically rebuild css" checkbox checked on your Design/Themes page. It should be unchecked in your production environment.
I'm not sure your memory/files/query_time are a result of styles. I.e. queries should have nothing to do with styles since they're stored in the filesystem, not in the database.
It's not clear to me what looking at query time/resource usage has to do with compilation of less => css.
I was in the debug menu and took a look at the logging, this basically shows you which steps takes a lot of time.
And styles compilation is just a name for another process but it does make my page load very slow!
Here is the complete list:
Before init
Memory Files Queries Time
556,384 16 0 0
Before database connect
Memory Files Queries Time
363,312 (919,696) 32 (48) 0 (0) 0.0003 (0.0003)
After database connect
Memory Files Queries Time
11,544 (931,240) 0 (48) 0 (0) 0.0003 (0.0006)
Session: before redis connect
Memory Files Queries Time
203,208 (1,134,448) 14 (62) 10 (10) 0.0025 (0.0030)
Session: after redis connect
Memory Files Queries Time
1,472 (1,135,920) 0 (62) 0 (10) 0.0002 (0.0032)
Cache: before redis connect
Memory Files Queries Time
26,712 (1,162,632) 4 (66) 5 (15) 0.0009 (0.0041)
Cache: after redis connect
Memory Files Queries Time
1,472 (1,164,104) 0 (66) 0 (15) 0.0001 (0.0042)
After init
Memory Files Queries Time
15,847,264 (17,011,368) 95 (161) 22 (37) 0.0344 (0.0386)
Before TPL
Memory Files Queries Time
992,472 (18,003,840) 17 (178) 561 (598) 0.1224 (0.1610)
Before styles compilation
Memory Files Queries Time
359,920 (18,363,760) 27 (205) 1 (599) 0.0035 (0.1645)
After styles compilation
Memory Files Queries Time
45,054,128 (63,417,888) 2 (207) 0 (599) 0.3542 (0.5187)
Start render location
Memory Files Queries Time
-44,679,984 (18,737,904) 7 (214) 0 (599) 0.0720 (0.5907)
[Block] [Quick links] Render begin
Memory Files Queries Time
277,096 (19,015,000) 3 (217) 6 (605) 0.0028 (0.5935)
[Block] [Quick links] Render end
Memory Files Queries Time
100,112 (19,115,112) 17 (234) 4 (609) 0.0022 (0.5956)
[Block] [Languages] Render begin
Memory Files Queries Time
3,808 (19,118,920) 0 (234) 0 (609) 0.0000 (0.5957)
[Block] [Languages] Render end
Memory Files Queries Time
84,296 (19,203,216) 3 (237) 6 (615) 0.0023 (0.5980)
[Block] [Currencies] Render begin
Memory Files Queries Time
3,432 (19,206,648) 0 (237) 0 (615) 0.0000 (0.5980)
[Block] [Currencies] Render end
Memory Files Queries Time
40,296 (19,246,944) 1 (238) 1 (616) 0.0006 (0.5986)
[Block] [FAQ] Render begin
Memory Files Queries Time
3,800 (19,250,744) 0 (238) 0 (616) 0.0000 (0.5986)
[Block] [FAQ] Render end
Memory Files Queries Time
43,848 (19,294,592) 5 (243) 0 (616) 0.0005 (0.5991)
[Block] [Logo] Render begin
Memory Files Queries Time
37,408 (19,332,000) 2 (245) 0 (616) 0.0004 (0.5995)
[Block] [Logo] Render end
Memory Files Queries Time
36,432 (19,368,432) 1 (246) 0 (616) 0.0004 (0.5998)
[Block] [Search] Render begin
Memory Files Queries Time
4,176 (19,372,608) 0 (246) 0 (616) 0.0000 (0.5999)
[Block] [Search] Render end
Memory Files Queries Time
61,224 (19,433,832) 6 (252) 0 (616) 0.0007 (0.6006)
[Block] [Cart content] Render begin
Memory Files Queries Time
3,432 (19,437,264) 0 (252) 0 (616) 0.0000 (0.6006)
[Block] [Cart content] Render end
Memory Files Queries Time
45,928 (19,483,192) 1 (253) 0 (616) 0.0007 (0.6013)
[Block] [My Account] Render begin
Memory Files Queries Time
3,432 (19,486,624) 0 (253) 0 (616) 0.0000 (0.6013)
[Block] [My Account] Render end
Memory Files Queries Time
207,816 (19,694,440) 8 (261) 0 (616) 0.0018 (0.6031)
[Block] [Top menu] Render begin
Memory Files Queries Time
6,416 (19,700,856) 0 (261) 0 (616) 0.0000 (0.6031)
[Block] [Top menu] Render end
Memory Files Queries Time
239,888 (19,940,744) 10 (271) 64 (680) 0.0153 (0.6184)
[Block] [Breadcrumbs] Render begin
Memory Files Queries Time
18,272 (19,959,016) 0 (271) 0 (680) 0.0003 (0.6187)
[Block] [Breadcrumbs] Render end
Memory Files Queries Time
55,336 (20,014,352) 2 (273) 0 (680) 0.0006 (0.6193)
[Block] [Uitgebreid zoeken] Render begin
Memory Files Queries Time
7,192 (20,021,544) 0 (273) 0 (680) 0.0000 (0.6193)
[Block] [Uitgebreid zoeken] Render end
Memory Files Queries Time
283,528 (20,305,072) 5 (278) 17 (697) 0.0572 (0.6766)
[Block] [Category side banner] Render begin
Memory Files Queries Time
3,448 (20,308,520) 0 (278) 0 (697) 0.0000 (0.6766)
[Block] [Category side banner] Render end
Memory Files Queries Time
52,576 (20,361,096) 0 (278) 0 (697) 0.0004 (0.6770)
[Block] [Net bekeken] Render begin
Memory Files Queries Time
3,432 (20,364,528) 0 (278) 0 (697) 0.0000 (0.6770)
[Block] [Net bekeken] Render end
Memory Files Queries Time
99,648 (20,464,176) 0 (278) 0 (697) 0.0003 (0.6774)
[Block] [Category banners] Render begin
Memory Files Queries Time
3,808 (20,467,984) 0 (278) 0 (697) 0.0000 (0.6774)
[Block] [Category banners] Render end
Memory Files Queries Time
5,376 (20,473,360) 0 (278) 2 (699) 0.0009 (0.6783)
[Block] [Main Content] Render begin
Memory Files Queries Time
3,432 (20,476,792) 0 (278) 0 (699) 0.0000 (0.6784)
[Block] [Main Content] Render end
Memory Files Queries Time
1,235,320 (21,712,112) 28 (306) 0 (699) 0.0382 (0.7165)
[Block] [Mijn profiel] Render begin
Memory Files Queries Time
184,072 (21,896,184) 0 (306) 0 (699) 0.0009 (0.7175)
[Block] [Mijn profiel] Render end
Memory Files Queries Time
18,704 (21,914,888) 2 (308) 0 (699) 0.0006 (0.7181)
[Block] [Extras] Render begin
Memory Files Queries Time
4,176 (21,919,064) 0 (308) 0 (699) 0.0000 (0.7181)
[Block] [Extras] Render end
Memory Files Queries Time
14,064 (21,933,128) 1 (309) 2 (701) 0.0010 (0.7191)
[Block] [Klantenservice] Render begin
Memory Files Queries Time
3,432 (21,936,560) 0 (309) 0 (701) 0.0000 (0.7191)
[Block] [Klantenservice] Render end
Memory Files Queries Time
17,080 (21,953,640) 1 (310) 6 (707) 0.0018 (0.7209)
[Block] [Become a seller] Render begin
Memory Files Queries Time
3,432 (21,957,072) 0 (310) 0 (707) 0.0000 (0.7209)
[Block] [Become a seller] Render end
Memory Files Queries Time
19,904 (21,976,976) 2 (312) 2 (709) 0.0008 (0.7217)
[Block] [Contacteer ons] Render begin
Memory Files Queries Time
3,432 (21,980,408) 0 (312) 0 (709) 0.0000 (0.7217)
[Block] [Contacteer ons] Render end
Memory Files Queries Time
8,616 (21,989,024) 1 (313) 0 (709) 0.0002 (0.7220)
[Block] [Informatie] Render begin
Memory Files Queries Time
3,432 (21,992,456) 0 (313) 0 (709) 0.0000 (0.7220)
[Block] [Informatie] Render end
Memory Files Queries Time
10,296 (22,002,752) 1 (314) 1 (710) 0.0006 (0.7225)
[Block] [Copyright] Render begin
Memory Files Queries Time
-190,560 (21,812,192) 0 (314) 0 (710) 0.0002 (0.7227)
[Block] [Copyright] Render end
Memory Files Queries Time
6,400 (21,818,592) 2 (316) 0 (710) 0.0003 (0.7230)
[Block] [Footer menu] Render begin
Memory Files Queries Time
3,808 (21,822,400) 0 (316) 0 (710) 0.0000 (0.7230)
[Block] [Footer menu] Render end
Memory Files Queries Time
8,632 (21,831,032) 0 (316) 2 (712) 0.0010 (0.7240)
End render location
Memory Files Queries Time
-20,000 (21,811,032) 0 (316) 0 (712) 0.0002 (0.7243)
After TPL
Memory Files Queries Time
151,056 (21,962,088) 12 (328) 0 (712) 0.0058 (0.7301)