When should wheel bearings be replaced on L300?

You really don't have to worry about them until they start to make noise. Could be at 40,000 miles or 140,000 miles on the same make and model of car. Also if you take your car in for an alignment or other service and they find bad wheel bearing.

Thanks for the quick response. I just came from Firestone. They did an alignment for me and told me the left driver side was "going bad." Wanted $366 to replace. I tried to get them to tell me how bad but they would just say, "Well, you don't want the wheel to fall off." I'm trying to figure out how soon I should get it down. It is making a little noise, but I thought it was the tread on my tires. This model seems to have more car noise, anyway, so not sure what to do.

only when the noise is very significant and you can barely hear yourself talk in the car that's when i would get it changed..... had that on an opel zafira.... waited until i couldn't stand the noise anymore and got it changed caus it is expensive... wheels didn't fall off for me and i didn't notice much difference in driving quality

if your strapped for cash don't change it but if you have enough money you might aswell

Thanks, everyone. The noise is quite loud, like you said...can't hardly hear yourself talk. I just took it back to have them do it. I figure, better safe than sorry. I have to drive 100 miles in a few hours. Thanks, again, for all of your help!