Simple.
A candle with a hole down the middle into which you can stick wicks of various lengths.
The candle holder holds these wicks in little trays marked with their burning time. 30 minutes, 1 hour, 2 hours etc.
When you're ready to burn the candle, select the wick from the tray marked with the time you want, pull out the old wick (the last 1/8th inch of which doesn't burn to hold the hole open) put your new wick in and light it.
It's the simplest solution.-- doctorremulac3, Jun 17 2014 What prevents the wick from slipping down inside the candle as it melts?-- MechE, Jun 17 2014 The wax coating on the wick melts and merges with the candle wax. Is that your bone and reason for said bone? If so it's not a problem.
The wax coating on the wick is also necessary to give some stiffness to the wick when you poke it down into the hole. There's also friction between the wax on the wick and the wax in the hole.-- doctorremulac3, Jun 18 2014 Erm, forgive my ignorance, but aren't all candles self-extinguishing?
Not playing this meme.-- not_morrison_rm, Jun 18 2014 Once they burn out. This is for a candle that will burn for a set amount of time then stop, being able to be re-lit to burn another set amount of time.
You don't have to worry about putting them out at the end of the evening which is less hassle as well as a safety feature.-- doctorremulac3, Jun 18 2014 Not my bone.
I'm also not certain the wax wouldn't slip past the wick and fill in the hole below it.
Maybe the candle comes with a small graduated drill and scissors apparatus and a continuous piece of wick. You drill the hole out to the right depth, insert the wick, and trim to height.-- MechE, Jun 18 2014 Damn those phantom bones. Come out you stealth boner wherever you are!
Just kidding.
That would work, but I've moved beyond this and onto the dial-a-candle.-- doctorremulac3, Jun 18 2014 random, halfbakery