I almost never manage to reuse birthday candles — there's always too much going on at the moment to remember to save them, and then they're not as beautiful when they have burnt tips. But for a recent birthday party I used Betty Crocker 4.25" candles, and when I was cleaning up, I came across the used candles. Irealized that given how long they are (very long still), all I had to do was to snip the black tips off, and they are seriously good as new. Nice!
If the blow-out's quick, this hack might even work with regular birthday candles. Also, if you light the candles in another room and bring the blazing cake to the crowd, no one will notice the burnt tips in the first place.