Bought this a few years back for use with my motorcycle which was giving me some electrical grief and sometimes draining my battery. I've been keeping it charged up in my backpack for the past couple years but didn't end up having to use it until this week when my bike was gonna leave me stranded. It worked like a charm and got me back home.
It seems to hold its charge very well and I only plugged it in every couple months to top it up but it probably didn't need it. The only downside I have noticed is that in my backpack it can sometimes get bumped and turn its flashlight mode on, which drains the battery. I think that has maybe happened twice and luckily I noticed it before the battery had completely died (at which point the flashlight would turn off and you'd have no idea it was completely dead). Just be careful how you stow it so that you don't accidentally find it drained when you need it most.