Heck yeah, run it till she absolutely refuses to start again, lol.
Seriously, though, I can feel your frustration with having to spend too much time on the engine. At some point, you've got to factor in how valuable your time actually is then make a decision. Do you want to pull the motor, tear it down to the block, and rebuild it yourself (which, btw, is something you COULD do), or sell it like it sits and spend the cash to buy a new one? The catch is, a new 20hp is gonna run around 6k isn't it? For a lot less than that, the one you've got could be "new".