It depends on what I'm playing with at the time. Lately I have been using the Rossi F200s a lot. I have 4 of them that are matched for weight and balance. Two of them have the same string at the same tension (ToughGut @52 with 10% pre stretch), the other two have Pacific Classic (@55 with 10% pre stretch) with one set of the string treated (a process that I have patent-pending on) and one untreated for comparison.
If I'm playing with something else (Dunlop Max200g or 300i usually) I have three matched rackets.
Depending on who I'm playing/hitting with, I may put in a couple wooden rackets or something else fun to take out and whack a few balls with, like a Head Graphite Pro or Composite Edge.
If I get back to playing tournaments in the future I will likely go to 5-6 matched rackets in the Tourney bag so that I won't need to restring no matter what happens (I'm not a string breaker, but I also don't like to take chances in that sort of situation).