"my experience is that if you fully format a pen drive you have something like a 10% chance of permanently corrupting it, making it unreadable".
*My* experience tells me you should get better quality UFDs. Or at least stop using the promotional ones you get for free. Many of those are laughably *under*-provisioned: a 16GB UFD actually containing a 512MB flash chip...? Yeah, I can see how well that will work! :-D
No UFD -- indeed, no non-ROM storage medium of any kind or capacity -- enters my service without at least a couple of full drive write/reads with integrity checking, if I can help it. Very few fail this. But at least those that do take no data with them.