Do pools need drains?-A study on the subject

[mustBnuts]

We installed a 13 x 30 fiberglass pool on a do-it-yourself basis in '05. We decided not to install a main drain since the pool will never be drained anyway. We didn't want to worry about it leaking or entrapment.
As far as circulation goes, there are 2 inlets in the shallow end and 1 in the deep end which keep things pretty well stirred up. It needs vacuumming 3 or 4 times a week, which is about par, I suppose. 1 skimmer in the deep end is all that feeds the pump. There is a sump line under the pool to pump out ground water if it should need to be drained, a submersible pump could empty the pool fairly quickly.
Hindsight being 20/20, I wonder if I should have some sort of vacuum breaker in case the vacuum hose gets blocked?