Usually when I am just cruising, I may be in the 2200 to 2700 RPM range. Knowing that lugging an engine is worse for it than revving, I downshift a couple of gears if I need to accelerate, usually over 3000 RPM. To me it is like saving revs in the bank for the good times when I want to hit VTEC to redline. Am I hurting a high revving engine like this by running it at the lower revs during cruise?

 

I don't think so. As long as you are downshifting when you need to pick up speed quickly and avoiding the "lugging" part, what you are doing is perfectly OK and will definitely make your engine last longer, in addition to saving fuel.
Cheers,
Daniel