+1 on overkill. I have the Durano Plus, which is not quite as puncture resistant as the Marathon Plus (but close) and have yet to get a flat. The liners won't kill your tires, but will definitely make the ride more uncomfortable.
BTW, the tires will get easier to take off and put back on. Ride them for a while. Eventually you might be able to do it with just your hands and no tire lever.