Yeah, my cordless ones quit halfway through a fade once. Had to dig out the old plug-in Wahl set I keep in the back of the drawer. It's clunky and the cord's a pain, but it always works. I also keep a spare blade set and an extra power cord for it, because that's usually what goes bad on me.
Read somewhere that battery tech in clippers just hasn't caught up to the old plug-in motors for reliability. @richard_webb Your story about the cordless ones quitting mid-fade proves that point. Sometimes the old, annoying cord is just the smarter tool for the job.
Understand where @aaron_perry is coming from about battery life, but MODERN clippers with lithium batteries can be super reliable. I keep a spare battery charged and ready at all times for my cordless set. That way if one dies, I just swap it out in seconds. Also having a basic plug-in backup in your kit is a SMART move for total peace of mind. Regular blade cleaning and oiling prevents most issues before they start. It's all about setting up a system so you're never stuck running to the store.