Absolutely agreed. If I was doing 40+ hours a week of client work, I'd have the margin (and financial need) to work with multiple clients in any given season. But in addition to a full-time gig, I just can't swing it.

Most the work I take on is shorter design/direction gigs with 1-3 week timeframes. In the gaps I take my 15 hours and use it for personal work. But again, all unique to my situation.