For rare stuff, I don't know that timing is as important, but early spring is when most photographers are getting their kits in order--and wallets open a bit more. For wet platers getting cameras built now for the spring, winter is a good time to buy a lens, but your Petzvals may be a little short to catch that crowd. I guess I'd just list them and see what happens. The Grimes flanges won't bring any more money beyond the cost of the flange, so I wouldn't bother. Lots of us have a board with an iris clamp for small stuff like yours and small lenses are easy to jury rig anyway. Good luck with your sales.