I can pretty much predict when I'm going to break a string.
I just play at home now and have become lax about changing them as often as I should, problem is I'm a whammy nut so I put quite a bit of stress on my strings.
After about 3 weeks (and this is actually pretty good) I'll pull the bar up and "ZING", there goes my high E string. I'll pretty much expect it though, and this is when the strings get changed.
Right now my 520 is sitting in its stand with broken E and B strings. Just too lazy to change them at the moment. :-)
As Rich said, change them more often and you won't have a problem.
When I was working as a tech for Paul Plumeri the strings on his guitars got changed every 2 gigs, every gig during the summer if we played outdoors or in a club with no AC.
And he plays vintage Strats and Les Pauls, so we're not talking about strings being put through the stress of being pulled up a major 4th like with a FR trem. :-)