There a reason why Nikon discontinued these? was there a problem or are they just trying to sell the (900, 910? Ive had one for a number of years now with no trouble at all and was thinking of picking up a couple more but I was wondering if maybe they had a problem with them and I got lucky with mine.
People were killing the flash by shooting too much in a short period of time, and overheating the inside of the flash.
The plastic case is a heat insulator, and traps the heat inside the flash. There is no air vent or metal heat sink move the heat to the outside.
So in the 9xx series, they put a thermal sensor, that will shut down the flash if it got too hot. Or was that the 810?
At any rate, pay attention to how much you shoot in a period of time, and you will be just fine.
If you have to shoot a lot, get a 2nd flash and rotate, to give the flash time to cool down.
With digital it is too easy to shoot, you just press the shutter button. And you don't have to change film cartridges after 36 shots. And it does not cost you $1 per shot. So people shoot . . . a LOT. A classic example is wedding photography. In the film days, it used to be less than 100 shots. Now you see people talking about 1,500+ shots. That flash is being used a lot more and a lot harder.