The only calandar part of an enstrom is the lamaflex bearings, they are 6 years, the MRB's are on condition but usually last at least 10 years, most of the other parts are on hours, MRGB & TRGB 1200hrs, Engine 1500hrs etc.
The enstrom is a good bet if you are only going to do 50 hrs a year or less as a personal machine - the early ones pre 280fx are a bit old fashioned compaired to the Robinson but safe as houses. Running costs are a bit more on fuel than a r22, a bit less than a R44.