Another thing that I don't like about incandescent black light bulbs, compared to CHEs is Murphy's Law. Murphy guarantees they will burn out not only early and often, but that your black light bulb will burn out right after you fall asleep on the coldest night of the year, leaving your tortoise too cold all. night. long. Buy plenty of extra bulb if you still decide to go this route. You'll need them.
By contrast I have a CHE that I have been using continuously since 1991. It is in use right now. The only time I've had a CHE burn out is never. I once dropped one and broke it, and I overtightened one and broke the metal base portion off in my fixture, but the rest of them still work as good as the day I bought them many years ago.
CHEs are also more efficient. Where an incandescent bulb gives off 20% light and 80% heat, the CHE gives off 100% heat. This means you get more heat for the same wattage with a CHE. Or it can mean the the CHE will run less often because it makes more heat if you run it on a thermostat, as you should.
I use them in my outdoor pens. I only need them a few nights a year because it never really gets too cold.
I like them because they give off a faint glow that I can see without having to open up everything and disturbing the tortoises.
They are on timers and they last me no more than a year each. As Tom says, they do burn out. Usually right when they turn on. That would be the con.
The plus is that they are cheap and don't need any special housings, etc. Great for adding a little heat inside or for added heat outside, if you live in the tropics and your tortoises won't be harmed by not having heat for a night........