I've had my Smok Koopor Plus 200W for almost a year now. The only problem I've had is that the magnets that hold the cover on pop out from time to time. As that has happened I've put a film of super glue on the inside edges of the mounting holes as I replace them. Be sure and use a plastic bag over your finger as you press them in or the glue will do as super glue does and penetrate your skin.
Other than that, it's been a great mod for use around the house. When I leave to go somewhere I grab a small mod like the iStick 40W, but around the house it's the Koopor or the RX200S. The dual Sony VTC4 batteries in the Koopor give me two days of vaping time at 10W and that's several hours more than the three Sony VTC4's in my Rx200S provide.