I've had the same problem and it just began recently. As in the past couple of weeks. If I log in and then come back a few hours later to see what's new, I find that I've been logged out and have to log in all over again.
How is this even such a big deal? Are you exceptionally lazy? I am pro security in general, and I don't find having to log in again once every few hours to be that big of a deal.
If it really bothers you, why not use a free password manager like Last Pass? Mind, in my case, I still get the CAPTCHA on re-login attempts.
Some people seem to think not being logged in will somehow affect their ability to seed/download their torrents, but that is not the case.
Yes, I am exceptionally lazy. As you are exceptionally rude.