As a typical trend the more expensive the better, but after time you'll get your own judgement on paint. Extreme (I know we live in Britain, but extreme in the relative sense
) weather conditions will ruin most paint as well as age.
A test I do is...
Drop it from shoulder height onto a hard surface, if it breaks it's too brittle.
Throw it hard at something, if it bounces or doesn't break it's not brittle enough.
Finally, shoot it, and if it produces the accuracy you're acquainted to with your gun, it shoots well enough.