I've found having 2 or 3 different partners that you play with often works well. One can be your 2.5 friend and then pick up a 3.0 partner also. Then if something happens to one you aren't also out for the season.
As for only playing with those at your level or above...now lets think about this. If you only play folk at your level then you won't pick up the experience necessary to get to the next level. If you only play your level and above then how would those folks below you play someone their level and above without playing someone your level. I like playing a bit of every one, even throwing in a singles match every now and then even though I'm pretty hopeless at singles. When I open up to play people at my level, above and below me I can get a match every day! Is this great or what.