I guess that’s a benefit to having a shopfront within a bigger name like Etsy or BigCartel. Your shop is just a shop and not necessarily attached to a blog where the last time you posted can be a deciding factor on when you buy.
The last post being in 2016 combined with that post about it being a quiet/personally busy year means I personally would move on. I’d have a niggle of hesitation starting at ‘last posted a month ago’ and just plain not if it hit six months.
It also depends on what stock they have and whether I’m really wanting something particular that I can’t find elsewhere. In those sorts of circumstances, I would probably still get in contact first.