accounts aren't locked automatically, if that's what you mean...

If you abandon your account, but remember your password, there is no time limit... you can come back whenever you feel like it.

If you did forget your password, but staked an address in an old, unedited post, you can prove your identity by signing a message, and your password will be reset.

If you did forget your password and didn't stake an address, it depends... Maybe you never changed your e-mail, maybe you posted a website you own, maybe you posted a twitter handle, maybe you have a dedicated home ip that's somewhere in the logs... So maybe you'll be able to recover your account... But don't get your hopes up.

Bottom line: stake an address AND don't forget your password... Especially if you're taking a break from bitcointalk, but you think there's a chance you'll come back in a far away future.