How long should it take for my PRs to get merged?

I’m on a small team of about 8 people. In between tasks I go take a look at the list of PRs and try to review whichever ones I can. But I’ve noticed that there are 9 total, 3 of them are on hold, one of them I commented on, and the other 5 are mine. The oldest one is 3 weeks old. My concern is that by the time someone reviews it, or raises a concern it’s no longer fresh enough for me to remember.

I understand this for larger PRs, some of my PRs are quite large (we are working with legacy code, my first step is always to get existing code under test and this can take a while). But some of my other commits are really small, only affecting a few lines.

How long should it take for my PRs to get merged, is this a problem with my team?