My 20' seafari has always been on a single axle trailer, since new. That being said, when the time comes I will replace it with a double axle trailer as it's getting old (1991) and It's now being trailered exclusively (as opposed to previously just winter storage, and only two seasonal trips to the ramps a mile away)... Now it sees weekly use and highway driving
Second trailer has lasted longer than the first, so I feel I'm on borrowed time.