life span of any gun can be questionable... metal ones can last long.. or if they're shitty casts the pot metal can just snap, just as easily as plastic.
Some plastic guns (nylon fiber) can be stronger than some metal guns... all in what you choose.
No gun will likely survive you falling onto it... they'd all likely snap in half... usually at the stock hinge/mount.
Other things that can go horribly wrong are screw holes stripping threads or screws snapping off inside, though screw snapping off is not the end of the world you can drill and retap... a receiver shattering is end of the line. How often does that happen? pretty rarely.
In terms of mechanical bits... you want to aim for the most TM compatible so you get the most available parts on the market if things go wrong, like gearbox shells, gears, hop up units etc... all the guts are interchangable with new stuff, as long as the receivers and shell are made to the proper standard. Things just drop in with minimal work.
Some brands are oddball no matter what you do with them... their parts are sort of TM spec but just slightly off so that when you replace it, shit doesn't work quite right.
Since you're looking at AKs someone with extensive AK knowledge can help you, since not all guns of any one brand are awesome, there's always a gun someone else makes that's slightly better than the other.
If you want affordable metal AK, then look at CYMA. It'll likely last longer than you want to keep it as long as you don't use it as a pry bar. They are nicely TM compatible, lots of parts fit and lots of parts are available. It's nicely priced so that if you do break it externally, you can walk away from it or salvage what's good and sell the bits off to fund your next gun.
I futz with V2s, V3s and V6s. I could be wrong... but probably, most likely not, as far as I know.
Last edited by lurkingknight; October 7th, 2013 at 21:27..