This is for an old ( 1998 ) Klein Mantra that I've acquired recently.Apparently the length between the eyelets is 170mm which is uncommon among the different rear shocks out there now.Cane Creek still makes a version of the Cloud 9 for it and I could always have Push Industries rebuild my Fox Vanilla X.The thing I'm most concerned about is longevity-I want to know I'll be able to have a functioning rear shock for this bike a few years down the road.

1.How durable are these shocks ? Which shock lasts longer ( most milage before a rebuild ) ?

2.Is it true that an air shock like the cloud 9 either works or it doesn't,but even if the Vanilla X is completely worn out,the spring will still do the job well enough to ride ?

3:Is it true that the Cloud 9 is much easier to rebuild than the Vanilla X,a do it yourself type of rebuild ?

4.I know the Cloud 9 weighs about 200g less and when set up correctly it offers superior performance,but any other things I should know ?

5.If I decide to stay with the Fox Vanilla X,I'd probably try to find a 2nd one used to be able to switch back and forth during rebuilds and as a spare--would it be really hard to find it in the 170mm length ?