[thstone]

There is a lot of variability in suspension ageing because of variability in use. With that being said, the stock suspension can need attention as early as 75K miles. By 100K, a lot of parts can be worn. At 125K miles, it definitely needs a refresh. I replaced my suspension at 110K miles (with Bilstein PSS9's) and the stock shocks were toast at that point.

There are quite a few cheap eBay coilover manufacturers. Some people have a good experience, others have horrible experiences. The racing folks will say that they're crap because the shock performance will be fairly poor. But if you're just driving around town with a canyon run every once in awhile, you may not notice (or need) true coilover performance - maybe all you want is to be able to adjust your ride height.

There doesn't seem to be any real consensus on cheap coilovers - for every positive result there is an equal and opposite negative result. Its kind of a situation of taking your chances and hoping for the best.

If you want good performance, reliability, and longevity, then go with a known brand as Johnny Danger recommended. You'll pay more up front but you'll get very good performance and not have to worry about having to replace them in 2 years.