Is it really necessary to have your "limit"?

[Sully]

I play mostly limit as a part time player, and have probably moved up faster than is advised. At the same time, I have never been shy about moving down. Or all around. The bottom line is that I don't have a certain limit that I play, and each day, I look for good games, decide where I feel comfortable, and get in there.

For example, here is my play for the past two weeks:

30/60: 466 hands
20/40: 498 hands
15/30: 1,539 hands
15/30 (6max): 384 hands
10/20: 31 hands
10/20 (6max): 617 hands
5/10 (6max): 329 hands
5/10: 93 hands
2/4: 41 hands (first Pokerstars session)
NL$400: 238 hands

I would have to say that my main game is the 15/30, and the 10/20 6max is becoming a larger part of my play each month. My best game as far as winrate is the 30/60, but I have only played about 19K hands at that level(vs about 75K at 15/30)....I'm still not convinced that I'm a winner there, and I just don't have it in me every day.

Do any of you have a similar approach?
Is there a reason I should focus on a certain limit and stick to it until I am ready to move up permanently?
Is this some form of poker ADD?

Any thoughts would be appreciated.