When mechaninc is replacing a bad alternator, how long should I expect it to take?

It should not take more than a couple hours. You have to figure in the time it might take to have the part delivered since most shops will not have an alternator in stock. Also it is good to plan for some time to allow the technician to diagnose the problem to be sure the correct part is being replaced and your problem is fixed correctly.

The book time to replace the alternator on a 07 Camry 4 cyl. is 1 hour. If the engine is hot it will take longer to let it cool before you can touch it.