Echoing what's been said - anything mechanical suffers from wear and tear. Even electrical stuff can suffer from it it seems, electromigration I think it's called? Not sure on it, but I think that the electrons (especially in overvolted components) can erode the contacts.
But anyway, yes, it might be time to get a new optical drive, though I wouldn't expect yours to be going after only a year and a half. I have 2 24x CD-drives yet, both of which see fairly regular use, and they still work; both are at least 4 years old.
For a new drive, the Liteon 16x/48x DVD-ROM seems popular; I like mine.
