Personally, I don't. The guy (or girl) who signs off the fix/repair/replacement is qualified to do so. It really is as simple as that. The car analogy doesn't apply as firstly our techicians have better training, secondly they are more closely monitored (by the user (Me and my crew), the customer (the airline) and the regulator (like the CAA)) and lastly and most importantly, the people who I have come in contact with have a genuine sense of pride in the job they do. I'm sure that there are exceptions but I'm a satified user.
PM
Don't forget, if it all goes wrong, lots of people will be beating their way to all of the engineers who have signed the Tech. Log (Maintenance record).