Best time for Bass Maintenance?

Hi All,
I have a question that I hope some luthier types can give an opinion on. What is the optimum time of year to get some maintenance done on the bass? In the winter, when the wood is contracted, or in the spring or summer, when the wood expands? I''m talking about French polishing or touch up cosmetic work, revarnishing, sound post adjustment and bridge and nut adjustment. I realize cracks and other emergencies require immediate attention regardless, but I'm just talking about some standard maintenance things.
Ok, maybe more than one question. Is premixed French Polish
(like Bullseye's) any good or is it better for a DIY to use varnish flakes and denatured alcohol? And what is the proper ratio?
(i.e 1 oz flakes to 4 oz alcohol, or thinner?)
I just moved from the relative humidity of Virginia to the dry cold of Colorado, and I am worried about the finish on my Bass. Seems a little dry and flaky in some small spots.
Thanks for your opinions.