I haven't used a piezo igniter on a wilderness trip. Guess I'm a bit 'old skool' with my Bic in my pocket (and spares tucked in everywhere).

I've had some piezo igniters that wouldn't quit. Some of the long-nose BBQ/fire lighters kept sparking (and starting the BBQ) long after the butane ran out. A couple of different ones got left out over winter, under snow and snowmelt. Just for laughs, I dried them out and scraped the rust off the 'points' and, voila, they sparked again.

I wonder if higher elevations (thin air) makes it harder to create a hot spark (which is basically a tiny plasma arc AFAIK). Perhaps the gap needs to be adjusted?