You can drop a claim and claim something new at any point.
If you claim a love triangle then all your fics would have to be about the triangle in some way, no just having two of them in it and not at least referring to the triangle somehow. You might be better off just claiming one character if she/he'll be in all the fics. But as long as whatever it is you're claiming is going to be in all your fics then you can claim anything you want pretty much.