Most of those gaps are open year round, exception being Lincoln and Warren. Spoke with someone today that went over the App Gap and he said that it had plenty of frost heaves. Its supposed to snow tonight but that will be just a temporary setback as spring has definetly arrived. Certainly, the Middlebury, Appalachian , Brandon and Rochester gaps are rideable , just a bit bumpy.
BTW, There's a Grand Fondo scheduled in Middlebury around the weekend of June 14th. Events scheduled for a few days before and after. I believe its the first event of its kind up here. 3 rides to choose from on the 14th, the hardest being the infamous Lamb ride (Lincoln, Adirondack ,Middlebury and Brandon Gaps) at a little over 100 miles. Shorter routes of 70+ and 40+ also. Do a search for Middlebury Grand Fondo and tell your friends.