My car has an energy problem - the car often won’t start. I started by replacing the battery with the recommended Interstate, having the starter and charging system checked out and they seem to be fine, yet the problem continues, necessitating jump starts. I identified an earlier problem, a little light on the rear view mirror that can stay on if not turned off, but that’s not it. The only thing on is the radio’s clock but I can’t remove the fuse for it as lots of useful stuff are on that circuit and it probably dosen’t draw that much anyway. Half of the mechanics i’ve seen recommend replacing the starter as it is hitting a flat spot and half day it is not related. The car has been garaged for years, runs great, and is immaculate, having only 40k miles. Any ideas on what is happening and what I can do to solve the occasionally dead battery and the necessity of having to park where my jumper cables might reach a kind Good Samaritan’s car? 
First things first . . .
Please post back the results of the parasitic draw test . . . I assume your mechanic has already performed that. What I want is the numbers, for example 500 milliamps
And you may be misguided in thinking the radio’s clock can’t kill a battery. Even small things like that can discharge a battery
Since it appears to be staying on after you shut off the ignition and take out the key . . . if I interpreted your post correctly . . . that is indeed a problem, and you’ll have to figure out just how much of a problem it is
Hence . . . the parasitic draw test
Get that taken care of, resolve whatever problems are causing an unacceptable parasitic draw, then start worrying about other things
Could be the parasitic draw is the only problem, or maybe the only problem worth concerning yourself with at this time
Thanks db4690. Traveling now but will try to have that test done this week and return with results.