We rarely cook chestnuts as a vegetable, I suspect because there has been no native chestnut crop in nearly a century, thanks to a blight that wiped out the American chestnut. But they are delicious this way (and can form the basis for a couple of classic turkey stuffings).
Chestnuts are best when they feel heavy; lighter ones have started to dry out, will take longer to cook, and may never become fully tender. Chestnuts are in season in the fall; I would not bother with them past Christmas.