45' is too long, because you need to upgrade your license to Commercial.
Work backwards from there until you find a length you're comfortable with.
Ours is 44.5', because I'm married to a go-big-or-go-home girl. We had a very humble TT toy hauler for 12 years. Now that our kids are grown and out of the house, we had two requirements: (A) more creature comforts and (B) separate garage for our dirt bikes so we wouldn't have to unload the bikes before we relax for the evening. These two requirements added up to a BIG fiver.