I suppose it depends how you get on and how much you trust the dealer. Reason I go to Infiniti Glasgow is I've been there for a few year now and I'm so pernickety about stuff and checking etc but I have every confidence in them especially David the tech. Speak to him all the time, he talks to you like a person not a company representative, the dealership don't charge you for what you don't need, if you do need something expensive they tell you to try and get it on here or elsewhere cheaper and they'll fit it etc, how you'd want it to be. I expect and don't mind David giving the car a punting, but I would not expect them to be 'clutch busting' it away from the lights and the sorts. Best thing is to find somewhere on recommendations and try it a couple of times see how you get on. I chose them through people on here and after a few visits and my own 'paranoid' checks (lol) later I knew the car wouldn't go anywhere else.
Even if I change my car and its out of warranty (as most 2nd hand will be besides the usual 3 month thing) I think I'll still take it to David and the other Glasgow techs. Note I didn't say Infiniti.... as its the person that gives you the confidence. I understand half the time you never see the person working on your car and they usually don't come out to talk to you...that's where they differ. Key to the excellence service that keeps me a customer.