Pretty much only times I've ever messed up my glasses bad enough to not really use them any more has been on metal festivals, I tend to take good care of them since I can't really see shit without them.
I fell down a hole once when it was dark oustide and I wasn't wearing my glasses for whatever reason, and I was sober even!
Think it was WOA 2005 when I found my glasses underneath my airbed in my tent, they were very flat and hard to use after that...
Now every time I go to a fetsival I take my older spare glasses, I might see a bit worse with them on, but then again, if I do fuck them up it's not my every day glasses that are lost.
Think my last pair set me back some 400 euro, nothing you can cough up a few times a year.
As for getting them -
If you have serious issues as I do, you need to have them specially manufactured, also cut to fit the specific frames you want, usually you'll wait 2 to 4 weeks after your eye exam and picking your frames.
I'd like to see the store that has a pair of glasses with my exact vision on them ready to go.