Most herbs would survive outside until the first frost, and it's not impossible that it wouldn't have occurred in late November. Sometimes the first coastal frost isn't actually until late December. Though we should probably keep in mind that Collinsport is a very, uh, unique location where every tree seems to keep its leaves all winter long.
So, one could presume every herb would always be available.
As for whether or not 18th century New Englanders would eat salad, I have no idea. However, the salad was supposedly intended for Josette, so she would perhaps have a much more diverse palette.
Though a salad consisting solely of bay leaves doesn't sound all that appetizing, no matter how one might dress it.