Reusing batteries?

Hi I wanted peoples opinion on reusing batteries

Ive just popped the pin on my Wismec Predator so its being refunded and most likely not buying another. Ive had 4 batteries rotating in it for just about 14 days. Could I use them in my old mod theyre mint. I know the usual info about married batteries etc and know its probably bettee to take the hit but i spent £32 on batteries which id rather not waste them.