Limited housekeeping, similar to DVCs schedule, is pretty common within the timeshare industry...some provide more, some less,
DVC is probably close to average. Free valet parking, on the other hand, is certainly not the norm for a timeshare, and since it is contracted out, we ar enot privy to what type of subsidy Mars may be wanting from DVC to coninue the service...it may have been completely unreasonable compared to the number of guests that use it.
While I'm sure
most DVC guests welcome having clean towels at least once during a four day stay. And actually, since you say you've split the four day stay between resorts, you did use more housekeeping per trip than the average DVCer. Maybe they should institute a minumun stay to eliminate that additional cost.