I have a 22re and shortly after I got it I took it to the dealer to look for a problem I couldn't find. The service mechanic set the idle at 850 RPM and set the timing by ear. He said for this engine 850 was best. It also has 200k miles on it so it's a bit loose. I ran it like that for about 6 months and then swapped in a EB 268 cam and left the idle at 850 and seem to notice a slight lope compared to before the cam. This could be timing again or just the sightly longer duration of the cam.
As far as problems at 1000Rpm, as said, gas mileage will suffer and over time the engine life will shorten but not much. It may live 6months- 1year less than if it was idling at 750. I am just using this hypothetically so no one jump on me about some calculation <img src="/forums/images/graemlins/smile.gif" alt="" />