The Brake Situation

I brought our van in today to have the brakes re-re-done.  

Luckily, they were very quick to take it back and fix the problem.  

So the brakes are fixed (again) but the mechanic said he doesn't know why the brake spring keeps slipping out of place... which doesn't sound very promising.  

Now I'm paranoid that the problem will return.  When I asked what to do if it happens again he just said that it shouldn't.  Which again isn't a huge confidence builder for me considering it shouldn't have done it two times before.  

So I'm really praying that the brakes don't go bad again, and that the van can just hold on without any major problems until tax return time!