DID is a good brand. A lot of people change sprockets at the same time as the chain. Maybe the dealer didn't do this before you got the bike: I would have a look at 'em for hooking, wear etc while you are at it. A bit more work and expense involved, but a good chain and sprocket set, well-maintained, adjusted should last at least 10,000 miles (depending on conditions, how you ride etc)
usually they come in sets, so not too much more expensive
NB, just read your post again, the dealer changed the sprockets, but probably with cheap ones, like the chain