Alright, so i bought a 2 day heat amp on 11/17/2016. Used it on that day. expired two days later. was a bit bummed about it but i got the 5* gear i wanted. Went to usables in inventory to see if it was still there. IT WAS! But i couldn't use it again which is what i would assume. Thought i had to buy another heat amp. But i didnt want too. So i just left it alone and didn't look in usables again for another week. Decided to look in usables today 11/24/2016 and it gave me the option to use heat amp again. Was dumbfounded that the game let me do this. so i used it. "Of course"
SO!!! i guess the the main question is
How many times can you use a heat amp?
Shouldnt it go away after it has expired?
After heat amp expires do you have to wait a certain amount of time to use it again like the spending limit when buying CE/
I've never used a heat amplifier, because heat has never been my bottleneck. But my impression, which the wiki corroborates, is that a heat amplifier can be used only once. Then there are two possibilities:
A. This is an error in the game.
B. This is a user error. You thought that you had only one heat amp, but forgot that you had another, and so on.
Either way, you seem to be happy. Cheers.