Since someone asked here is the exact quote...

"Your Avios stay with you as long as you collect, spend, purchase or share at least one Avios every 36 months — any longer and your Avios will expire and be removed, so remember to take action before those three years are up."

Note that Avios might claim some kinds of credits to your account don't qualify. I can't imagine how they might do this but there is a chance that they could take this position with regards to the recent debacle where many people had their points removed then reaccredited. This means you can't be certain that all debits or credits qualify.

Anyone with a BA credit card can easily solve the problem by making a token charge every couple of years. Those without should consider renting a car or booking a hotel stay and crediting the points to Avios since both of these are explicitly listed as qualifying as ways to collect miles.

https://www.britishairways.com/en-us...s-expiry-rules