When I started out, I played a lot of straight up chugging palm muted metal. And I broke lots of low E's and A's. As my touch became more accurate it happened less but still happened.

Now I break high E's and B's, usually due to practicing Albert King style bends, but not so often.

I keep my strings clean by using FastFret, I love the stuff.

But there's a lot of ofther factors too. Like heat, humidity, fluctuations in weather, even the chemical makeup of your sweat, condition of your frets, bridge type and condition, pick size and material, etc, etc.

As far as strings go I keep lots on hand and organize them in a shoebox by gauge and look it over every now and then to make sure I don't run out. But yes, occassionally I still run out. Guess that's just part of playing guitar. :o