My account is enabled for TFA because I'm a moderator of several games and one series. That's fine with me, and while I wouldn't have enabled it on my own, I understand the choice to make it required. However, on my only desktop computer, I only check the site once every week or so. Every time I come back, I'm no longer logged in. The site had never automatically logged me out before the TFA change, and since it's been a while now, I know it's a consistent problem. Is this intended behavior? I'm less inclined to use the site if I have to manually log in every time I come on.

Do you have a configuration to automatically delete browser cookies? That's the only thing I could think of that would be causing this unless this is a site configuration.

The site doesn't automatically log people out regularly, there's the occasional maintenance issue that requires a mass logout but those are very rare, and aside from stuff like that I never get logged out of the site. I'm not sure what could be happening that would cause what you're experiencing, but the problem is most likely on your end.

What browser are you using?

I use Firefox on Windows 10 & Firefox Nightly for Android. I understand it happening in the nightly build on my phone, but it's the same on my computer.