The county I work for has its own fleet maintance shop, diesel engine less than 60 HP they figure 6000 HR useful life, 60-100 HP they figure 8000 hours, and 100+ HP I think its 12,000 hours, but that included extensive work/money upkeeping, repairing, and even rebuilding them. In general I would say skid steers lead a rougher, shorter life than the average piece of equipment. They often are ran by the lower end operators, with less real upkeep/maintance then say a grader/hoe. If it was used lightly to ferry mulch and bushes it might be very good, if its spent life trying to do the work of a Jd650 dozer then no so much.
That's 3600 hours in 7 years, under 500 hours per year, so approximately 10 hours per week. Low for a daily money making machine, lot more then a hobby/amateur machine.