I've had my tst 507 going on 7 years. On the first trailer it was there 6 years and I replaced batteries one time. Not because they quit but because I figured they would. I leave them on the trailer year round.
When I bought this trailer I ordered a new color monitor w/repeater and replaced the batteries. I do carry spare batteries with me. I've never had any interference from another user and unlike a previous poster I would highly recommend them.
Danny and Susan wife of 53 years
2019 Ram Laramie 3500 6.4 4x4 CC 4.10 SRW
2020 Montana High Country 331RL