We are same day(if call comes in early) or at the latest, the next day or immediatly if the call is an emergency.  It is different for each clinic because they operate on different hours sometimes so you take that into account. Our moto is not to have treatment delayed due to broken machine(s). Of course this is sometimes unavoidable but for the most part it works very well for us.
  Our problem is the clinics are getting overcrowded and there is very little space to work when the satelite is open so there are times when we must work late into the evening.