I find that there are just few customers that want a estimate before doing any kind of work. The other ones, that have an expensive repair, I let them know about what the cost will be. Very rarely does it come in under the estimate and if it goes over I usually eat some of the extra time. If it takes less hours, then just "hang out" and tinker with other things on the lift. I wouldn't leave and charge them more hours than you were actually there. A couple places I go makes visitors sign in and out. Customer may not have a clue what you are doing but they sure can figure out labor hours. Then there are the other type of customer that completely trusts you and doesn't pay attention to anything, including the invoices. "Just make my forklifts work so we can run this operation smoothly, we have other things to worry about" I'm very careful not to do anything to screw up that relationship.