They're super fun of course, but one functional issue I found that I didn't realize before buying is that since they are basically like pieces of tapes, they stick in one place. (C'on, hear me out.)  This means that if you don't smile and put one one, the two ends of the mustache become unstuck when you do smile, and if you smile and put one on, a bridge is created in the middle of the mustache when you're not smiling or posing a serious/smoldering look.

In my experience, they're definitely not one-time use if you don't sweat too much.  But if you don't feel like re-using them, toss them after use since they're super cheap.  Remember, it's 3 packs of 12, so that's 36 mustaches in total.

Lastly, the fake hair strands can fall off and stick to your face or in your drink.  A minor thing, no problem.  Overall, 3.5 stars.