Yessa!
I live here. May weather can be very iffy in Maine. Spring weather is historically cooler than Fall weather. I'd go in September.
I live here too --- and I agree wholeheartedly with NKN. September.
Fwiw, we just finished a late September week at Samoset ourselves (September 23-29, to be precise). Weather was spectacular except for a drizzly first half of Tuesday. Anything and everything (charter sailboats, shops, fairs, restaurants, farmer's markets, etc.) were all still very much alive and well and conducting their business --- and there are certainly still
plenty of out of state license plates and confused-looking tourists around. Foliage is nowhere near peak yet (although this has been a strange year anyhow due to unusual drought conditions here). Generally, things don't really slow way down and begin to wrap up for the "season" until around Columbus Day, except perhaps that some of the big "Windjammers" not heading south for the winter may start their lengthy and labor-intensive "winterizing" process a bit sooner.
I would choose September over May, but Maine weather is always an unpredictable roll of the dice anyhow --- perhaps even more so
two years in advance.
P.S. If RCI will reveal unit identification to you, any top floor Samoset unit is less noisy and preferable to the lower two floors; equally true in every one of the three (wood, noise-transmitting) timeshare buildings. That may also be a factor to consider if you care and if you can accurately learn the respective unit locations from RCI. There are no "floating" week ownerships at Samoset, only fixed weeks so, in essence, RCI knows right now
exactly what (very few) units / weeks were "deposited" and now presented to you as available for "exchange". It might be worth your while to attempt to extract from RCI those two unit identifications / locations for inclusion in your decision process. The Samoset front desk absolutely will not (and absolutely cannot) do anything at all for you in regard to making any unit changes at (or after) check-in. Check-in to the timeshares is actually handled by Samoset Hotel (i.e.,
not timeshare employed) personnel and those Hotel personnel, although always very friendly and very competent, understandably will
not ever move any exchanger into someone's owned (but
not deposited for exchange) unit / week, even if it's vacant, without that unit / week owner's prior knowledge and overtly expressed consent --- which they will
not endeavor to obtain.