Yes. Don't quote me on this, but I seem to recall the maximum length is 32 bars, based on 4/4 time, which would make for 128 beats. I could be wrong on the length, although I am fairly certain there is a limitation. At least there used to be when Apple Loops were first introduced.
Agreeing with Eli, I do remember there was (is?) a limit. I just did a little research to see if I could find anything on the subject because I couldn't remember the length and I found NOTHING on the subject. Appears to be a well guarded secret.