I go for the Fall and Spring
If you don't get there early, it will take you almost an hour to go the last couple miles

First time you go, it takes a solid 2 days if you want to see everything

For more local MA shows
Mothers day weekend is Great Woods >> I go there as a Buyer

Last Sunday of the month is Amherst NH
Amherst NH Antique Auto Show
I Buy and Sell at this one
This is an EARLY show >> People out shopping at 6AM and earlier
Back to just a field by 1PM, I usually leave about 11AM