Is it better for your score to use each of your credit cards at least once in each billing cycle in order that the DLA remains up to date?
1. I don't know what a DLA is.
2. It's not necessary to use each card in a billing cycle. Your score doesn't look at how many cards you used.
Date of Last Activity? just guessing, don't know.
Probably from context, typically written DOLA or DOLU (last update) historically.
To answer that question, it doesn't really matter much. Many lenders will still update on a $0 balance, but not all. You'd have to let a card sit idle for a bit and see if they continue to update month after month... Synchrony for example is the big guilty party on this one. That said you can simply use it every three or even six months and as soon as it updates, you get all the pretty OK's anyway for the intervening months so it's rather whatever.