How long will a 6v Cat's Eye Cigar lighter last with 12v??

Indefinitely until you push it in.

I doubt it would be much different but I am not an electrical engineer. The heating is done by the resistance and once it gets hot it pops out breaking the circuit. Might just heat up twice as fast.

Until it burns out.........
Actually it should just heat up faster and pop-out sooner. As long as you don't hold it in it should be no problem.

faster and sometimes further. My brother converted his 53 2 door sedan to 12 volt when he changed the original engine to a 1955 265 V/8 back in 1958. he had a custom set of seatcovers installed and when the cigarette lighter was pushed in the red hot lighter poped out onto his new seat cover and burned a hole in the naugahyde.

I installed a cats eye lighter in the 48 and had smoke coming out the back (hot wire)...Whats going on here

Might be a short.

Chev - probably too small of a wire. Should be a 14 gauge wire which is "thicker" than the usual lighting wire.

You should replace the socket with a new 12 volt one from your FLAPS. The 12 volt one is larger than the 6 volt one. You can't charge your gps or cell with a 6 volt socket no matter what the voltage is. (you wouldn't want to do it with 6 volts obviously.)
The cat's eye is the cat's ass but just keep it for looks. Or maybe you can unscrew it from the element and put it onto a 12 volt element.

Haha thats funny...The element lasted 5.5 cigarettes. I went to Napa and got a new element. Screwed it in, the eye still glows and it works well. What a coincidence.

Did you light a cigar/cigarette, and a chunk was stuck to it when it was depressed? Does it do it with a different accessory like a spot light or cell phone charger?

After almost having a fire I left it unpowered,never will be used any way...Although there is no reason way it shouldn't be operational..I will change the gauge of wire