I have always used the right belt for the job instead of the 'one size fits all' link belts for the very reasons that you brought up, Robert. I will not even attempt to use one as the secondary drive on my drill press or on my Clausing mill, there is just too much tension on the belt when gearing way down into the slower speeds, where you need the best power transfer that you can get.
I don't keep extras on hand either. My drill press is 20 years old and is still using the original belts. My lathe has a new vee belt for its primary drive, but uses a flat belt for the secondary drive. My Clausing mill received new belts when I bought it two years ago. I do keep a list of belt sizes, lengths, and standard belt numbers on hand though. Easy enough to look up when I do need one, and they can all be purchased at the local hardware store except for the flat belt for the lathe.
Sorry guys, I'm just not sold on the link belts, especially at what they cost compared to the proper belt for the machine.