Whilst it was somewhat of a tease, I honestly believe that you're better spent avoiding the entry level lines and looking around for used pro-level cymbals. Almost everyone who starts out on the budget lines wants to upgrade sooner or later anyway.....especially when they gain a little bit of experience and their ears become acustomed to just how great the difference between a quality cymbal and an entry level one really is. There is much you can do to make a cheap drum kit sound better than it is, but it's not the same with a cymbal.....they pretty much stay the same forever. I always recommoned aiming for a good cymbal sound from the get-go. There's huge saving to be had by scouring the used market.....and if you're ever unsure if something is appropriate or a good deal, then you can always come back and ask us.
My main thing is that I haven't broken any cymbals yet, and I hear people say ZBT crashes only last a few months.
Cymbals don't have a "lifespan" per se. There are guys who've been playing cymbals that are 50 years old and never look like breaking them. I never think about how long a cymbal will last me when I'm buying them. I think about the sound I want and the setting I want to use it in and try to choose the cymbal accordingly. So I don't use a paper thin crash if I'm going to be slamming senseless it with a 2B stick, for example.
That's not to say a cymbal will never break, sometimes they just do. But a lot of the breakage I read about comes from the wrong cymbal being used in the wrong application......and quite often it's simply a matter of guys hitting them way too hard. More often than not, how long a cymbal lasts comes down to how it's used and treated.
I should also add that the reason we all hear of so many broken entry level cymbals no doubt comes down to several factors......like the fact that they are often used by less experienced players who haven't developed their touch or feel on a kit yet so tend to smash the bejesus outta them. And of the fact that being entry level, they simply don't have the same manufacturing techniques that go into producing them that a pro-level cymbal will.