I installed one in my 367 double roller chain engine.......in 1999. It's still in there.That was 100,000 plus hard miles ago.(stick-car)
I tore the engine apart 5 winters in a row for inspection, and the tensioner was doing fine.
I put one on my teener too, also with a double roller chain, and that was year 2000. That one has about 50,000 miles on it now.
The nylon parts didn't scare me; most 4-stroke motorcycles have similar systems.
I had my engine "line-honed", but they weren't very good at it, so I had to do something,lol.