Probably agree with most things said here and with most of what biggles said, HOWEVER, an R44 will not suffer the same "misuse" at a school as an R22. Most cut their teeth on the 22 and then having had all the heavy landings, over-speeds, spindle bearing wear from lots and lots of autos progress onto a 44 purely to type rate and take their friends up. Yes I know several people train in the 44 and therefore my last comments are not valid but most don't.
Doubt if you would ever get £250 per hour today for a 44. Seem to remember seeing some sort of "black box" that you could fit to your heli that gave you start stop times, engine temps, rotor speed etc. Now wouldn't that be handy??
Bottom line, if you can afford not to do it then don't or buy a second 44 with lots of hours and little calender time left and use that at the school at a reduced hourly rate and don't give a sh*t what they do to it :-)