@citoyen : as a matter of interest, how long did your strap last? Mine's 2 years old and I'm wondering when it'll go wawa.
Probably about two years, funnily enough. I can't remember. It started by only working intermittently then stopped working altogether. I initially assumed it was the battery but changing the battery did nothing, so I tried changing the strap and that worked.
I think it's entirely pot luck how long they last. Much like headphones.
Mine's a bit iffy just now. It has just gone through the washing machine, though, and that usually helps. After a ride I usually let it soak in soapy water in the sink while I'm having my shower, then I rinse it and get the water out of the press-studs.
Tightening often helps, but the adjustment system is so pestilential that I rarely do it.
I tried one of the 7€ Celestial offerings last year, but it only worked for 2 rides.