There's a reason the pro's do ten coats. The build coats for the obvious reasons of shine and depth, but any more will probably just compound the effort getting it all back off if you need to strip it. But the idea with ten is you lose a coat during a year from elements, and then ideally two more coats will go when you sand it to freshen up the varnish yearly at three coats to get it back to the ten number. (Oh yeah, you get to do this every year).
At the end of your maintenance coats, fill a small two ounce bottle or so with the varnish, and a Q-Tip and small piece of 220 sandpaper rubberbanded to the jar. When you have those dings, spot fix it THEN. There's a hole in the pool, and it needs to be fixed now!. If water gets under it, it's all coming back off. THEN, you have to use wet or dry sandpaper, because aluminum oxide paper will not work well sanding through tears.
Yes, three coats is a MONUMENTAL waste of time. Don't even bother.
30 coats you need therapy.
And after fifteen, again, a waste of time and varnish.
(I do this kind of work on some very high end boats, for an awful lot of money. Repeat customers albeit)..
