After 15-20 minutes the flippers on my standard coil LOTR SE would get noticeably weaker. Tried heat sinks (held on with thermal tape and a zip tie), which added about 10 minutes of full power time. Finally in addition added a pair of large fans left over from a computer case that did not need them, mounted on some custom brackets, and that really did the trick: Full power for hours of play.
I ran some wires to the backbox, and since I have a ColorDMD, I was able to tie into the aux power pass-thru on that board, but you can just run back to the accessory connector in the cabinet front (like the colorDMD already does).