Hey! I'm gel tech myself and I used sanding bands as well. I recently bought carbide bit (not the YN) and it is great! It dosen't get dull and goes on so smoothly - I ain't going back to sanding bands. I was in lecture about e-file bits and they said, that depending on quality of carbide bit it can last everywhere from 1 year up to 7 years.
I don't really know the manufacturer of my bit, only thing I know is that's it's made in EU. I would strongly advise against going for something that's made in China - I have heard the quality is just dreadful and longevity is about the same as sanding bands'.
I have heard the Atwood Industries and Kupa (American companies) make good e-file bits, check them out.
About YN carbide bit I have read many good reviews, however, some say it's overpriced and you can get the same qulity for better price.
As for starters with carbide bit - try to use it on training hand or tip with gel on top, to get the feel of it, then you can try it out on your self, once you feel comfortable you can do it on clients. For me it took about an hour to get hang of it. I personaly enjoy working with carbide bit so much more than with sanding bands.