The only tasks which I find stop me from working on my product are various administration and customer support chores. The one-time items like incorporation are trivial in terms of time-cost.

Being forced to step away from development has actually saved me more trouble that it's taken away. Being forced to take a breather to tally up expenses or polish up some documentation takes my mind away from the development task at hand and helps give me a better perspective on things when I return. On far more occasions than I'd care to admit, I'll find myself thinking about the 'absolutely essential' work I was intently doing to improve my product and realize it was either completely unnecessary or else could be done in a better manner.

Those insights would not likely be gained if I had been focused entirely on development. Mix it up.