I've had a liftmaster side mount on my 18' door for at least 5 years. Absolutely no issues with the opener itself. I love it.
I did have the tracks "adjusted" for a little more pitch such that the door closes easier. When there was no "slope" on the upper horizontal run, there were some times when the door wouldn't close as the liftmaster doesn't "pull" the door closed as a center-mount does, it merely releases the tension on the cable enable the door to slide down. This wasn't an issue with the opener itself, and since I adjusted the tracks, there have been 0 problems.

FWIW - I'm on my original two Genie center mount screw drives. House built in 1993. An occasional light bulb in the unit and an occasional 9v battery in the remotes. (1) 18x8 and (1) 9x8 insulated doors. Extremely quiet.
$125 a piece 23 years ago. Not sure how pricey they'd be now.
I've had mine for exactly a year now. Only complaint for me is the very short range for the remote.
I do have led outdoor lighting on the garage which could be the problem, but even with the led lights switched off the range is about 20 feet.
The myQ stuff works excellent though. Whatever band the myQ communicates is unaffected by led interference.
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I have two on my 8X10 insulated metal doors. Quiet, short range, no issues after a couple of months.
8500 good on 18x10.

I've had mine for exactly a year now. Only complaint for me is the very short range for the remote.
