I've gone thru 3 of the Garmin 'comfort' HR straps in 1.5 years. I was able to get one replaced under warranty. The instructions say to rinse the strap after each use, and to hand wash them with mild soap every so often. I haven't had any luck with washing the straps at all - both times I washed the strap, it refused to work after the washing/drying. First strap I ran thru the machine on 'hand wash' cycle, second one I tried just doing hand wash in the sink. No joy on either.

I've also had issues with the strap losing contact with my skin, especially after any extended rest breaks during a ride (i.e. works fine for 45 mins of riding, then I stop for 30 mins, then resume riding for another 45 mins and the segment after the rest doesn't properly register). I suspect the later is being caused by losing the moisture between the strap and my chest - probably just need to wet it down again when I resume riding.