How long to keep in fermentation cabinet?

In my few batches of beers, I have produced some amazing and some not so amazing (which just got drank faster) beers. Throughout this process, I have done no real sort of ferm temp control but Im seriously looking into building a ferm cabinet.

My process is usually to leave the beer in the primary for at least 3 weeks (if not longer) to help the yeasties clean up after fermentation - POST fermentation when the yeasts are taking care of their other business, is temp regulation as important? (I mean, can I leave the primary in the FC for a week and safely move it to another location that *may* have fluctuating temperatures?) I know that when it is racked to the keg for further aging, there isnt a whole lot of temp control, so It would make sense to only utilize the FC for the first week or so of fermentation. Correct?
Thanks
-Me

Once you've hit your final gravity, temp control becomes less important.

+1, but I would not want it to go above the high 80's.
Once in a while I will leave one out when I'm short on fridge space. I cover it with a damp towel to even out the temp a little and protect it from light. I have never noticed and bad effects from it. Same with bulk ageing meads, etc.