Drive axle shocks

Many shocks offer lifetime warranties. You should get at least 200K out of a set. The problem is the bad roads we have to drive on today. One pot hole and the shock will be over compressed damaging the seal. A tire wearing with chop across the treads is a good sign you have shock problems. Sometimes you can even see the shock leaking. Worn bushings is another sign.
Once you suspect a bad shock, I would pull it off. Then you'll know for sure when you compress it and it doesn't want to expand.

 

200k might work if you are strictly running interstate w/very little urban area's--if you run a lot of east coast cities or chicago probably not--I change mine at least once a year 150-175K--but I do LTL and Im in nyc philly&chicago 2-3x a month
Just my $.02

 

What brand of shocks is the best for the steeraxle

 

And what brand for the driveaxle

 

suspention life depends on road conditions, load, drive style... sometimes I see leaking shocks in a year of driving, sometimes shoks are rusty but still ok

 

Since shocks are not that expensive in the broad scheme of things, I just go ahead and change them out on an annual basis. Usually during one of the times I am rotating tires as well. As was stated, roads, especially during the winter months, seem to be rougher and rougher all the time. Shocks are not that expensive, so it just makes sense for me to change them out annually. That puts around 140,000 miles on them.