How do I know when to replace the fretwire on my guitar? Are there indicators(sounds, feeling, how it looks) etc?

yeah, look at the frets closely, if you see a lot dents or if they're running flat (like, really low profile) you'll know you need a new fretjob.

also, you can get weird sounding notes if there's a huge dent in one where it touches the string, frets can wear pretty fast depending on their quality.

I've been playing my '89 RG750 intensively but it's still in pretty good shape, fretwise, even though it's a 16 year old guitar. (I don't think the former owner played it a whole lot.)

Alright because ive been getting alot of fret buzz and i got my guitar teacher to check out the truss rod and he said that it was fine.

Just incase you were wondering it was only around $350 (Canadian) so I'm guessing that the frets can't be anything too extrodinary.

I imagine, so did you check out the frets closely? often the upper five frets are most sensitive to fretwear, if you see dents, or if they're going really flat, you'll know they're going to need replacement someday soon.

it's kinda hard to judge though, you might want to take it to a guitar shop or something. usually fretbuzz is caused by bridge or truss rod settings, not by faulty frets, or it has to be really fucked up!

So would I just any guitar shop with a tech.?

By the way I've had it for about 2 and a half years. Can fret wear happen that fast?