Trust me, my WIPs are always at the back of my mind, on my "to do list". We don't just easily forget something we put so much time and effort into, so readers truly do not need to remind us that our WIPs exist. If they haven't been updated in ages, best you can do is leave a comment about how much you like the story and leave it at that.
Re: What's the etiquette on asking an author for an update?
Trust me, my WIPs are always at the back of my mind, on my "to do list". We don't just easily forget something we put so much time and effort into, so readers truly do not need to remind us that our WIPs exist. If they haven't been updated in ages, best you can do is leave a comment about how much you like the story and leave it at that.