Hey,

The timing chain is definately a preventative maintenance thing. Not sure if your motor is an interferance motor? In other words if the chain breaks your valve might hit the pistons and could cause all kinds of damage depending on how fast you where going when it let go. Could break piston crowns, bend conecting rods etc. Long story short in an interference motor, a timing chain failure at spead is potentially a catestrophic event.

Wheel bearings in my opinion get a lot of wear and tear, other members may have diferent opinions than me (they are mostly certified techs and I am an accountant by trade and Mercedes Tech wanabee). Wheel bearings are not huge money and should at least be inspected regularly, not exactly a catestrophic event if they fail but could be dangerous if one was to seize up, could effect handling. Anyway, they spin really really fast, a lot and deserve some attention. One easy inspection, kind of a find it after it's a problem is to put car on jack stands and grab tire with both hands and give tire / wheel a wiggle, if bearings are getting worn you'll feel a little shimmy almost like a click, just a little play, indicates wheel bearings are getting worn. By the way, other problems could result in shimmy, ball joint for example. Another way to tell if bearings are getting a little worn is to feel the wheel for excessive heat build up.

Taking hub apart I am sure would be the best way to inspect for worn wheel bearings. Again, others on this site much more skilled than me regarding this subject.

Just some thoughts,
Thanks,
Joel