Pinging the Clutch

In my experience, the clutch will stand up to a fair bit of abuse. Some of the earlier models had weaker clutch springs which were upgraded on later models (sorry, don't know which ones) but it's easy to replace your stockers with aftermarket units, or even KX250 springs (like I did).
All the normal things you do to help preserve your plates apply, such as changing the oil often, as you have stated. Do that and you should be pretty well OK.

Cheers

Another angle to your question, you may find the KDX power delivery doesn't need the clutch work due to the 'flatter' power delivery. It should feel like you have more power available at lower RPM's. (settle down, I said FEEL like....)
Instead of fanning the clutch, I do a little jump on the pegs when I need some wheelspin. After I jump, (or hop) that takes alot of my weight off the bike, and the rear wheel will start to spin, I 'land' back on the bike and get a little 'jet' action as my weight 'lands' back on the bike. No clutch work, but it has the same effect.
It's a subtle and quick action. A quick push on the pegs, followed immediatley by a pull up on the tank/seat with my knees.

Seems longevity of the kdx clutch is about as varied as the 'right' oil to use.

I've never been on an mx-track, don't spend a lot of time fanning the clutch, but certainly do from time to time. I change oil every several rides or so. I use the clutch to shift rarely (not that that's a big clutch abuse issue).

Still, I've got thousands of miles on my bike and the clutch is fine.

When it comes time to maintain it, I'll likely use a different friction plate like the XR plates with much more friction material.

If you have steel plates over aluminum plates you'll find it serves you better. Check yours with a magnet if you aren't sure.

Craig's point is excellent. The kdx can be tuned to run so well for woods riding, you don't need to tear up the clutch to get somewhere. Just twist the right-hand thingy!

Oh..on the changing oil thing. Overfill it. Use 100ml or so of the quart (bit more if a liter) to flush the case after the dribbling stops, then dump the balance of the quart in. 700ml is the spec, but that will give you a lot of clutch racket...and heaven knows the kdx makes enough noise!! The 'overfill' will quiet it down some.

You mention 'quality' oil. General consensus is, you don't have to use a hi-falutin' oil (read: expensive) if you keep it clean..change it often! Motor oil is just fine. ATF is popular, although a read thru the archives regarding that issue may make you wonder about 7W ATF in a gearbox. There's a good deal of debate on the issue.

...like the 'right' oil!! ;)

I've been riding my kdx for 2 yrs almost exclusively in very tight, heavily wooded, wet and hilly Canadian Shield terrain. In these conditions, I beat the clutch pretty hard yet it still feels like the day I first rode it. Like cany says, overfill slightly with oil and replace after every couple decent rides. After washing the bike I also WD the cable and joints pretty good.

same here, I mostly ride in real gnarly tight woods, and I'm abusing the clutch like a mad thing, and on my 91 kdx it is probably the stock clutch plates and springs still. So long as there's oil in there, it behaves perfectly, no worries.