I get seriously bored with one party so I guess its changing for me...

Though I hate it when you literally form a party, set them up etc and then someone leaves/dies, taking all your equipment with them (FFIV is a massive culprit).

Also games where there are too many party members (FFVI) can make things difficult, i.e. trying to level everyone up evenly.

I like the 6-8 characters in a cast, you can stick with one good party but can also mix it up a little without other characters getting left behind.