The ECM and stereo both have memory and will put a very slight drain on the battery. The drain should be so slight that a test light between ground and the battery should barely light and in the day time it would not be bright enough to be visible. with a Ammeter .06 amps should be all you see between stereo and ECM.
Get one of those solar trick charger and put it on the dash if the truck sits outside. On a lead acid its best to charge often. Not sure if the Optima is the same.
Never cared for the Optimas because of all the weird crap I hear about them that sometimes include poor charge retention in temperature swings. Early death at 2 years. They have their place I know but the Duralasts I have run in all my cars and trucks for the last 5 years have as yet to let me down even when they sit for weeks at a time. I have a 454 Sub sitting in my drive that has not been started in 2 weeks and I know it will fire right off first try. My wife has left lights on over night to the point no lights would come on and a charge and it was fine and doing great 2 years after that when I sold the truck (the battery was 5 in that truck). Personally if you don't have some weird sideways mounting requirement or a venting issue with mounting in a enclosed space save your money and get a conventional Lead acid.
