American Express Membership Rewards - How long until an inactive ICC card gets cancelled?

I hold a green International Euro Card that's free for life. I don't really have any use for it, but I'd like to keep it in case I ever decide to cancel my shinier IEC card. How often should I charge something to this card in order to keep the account alive?

I never heard about an Amex card beeing cancelled due to lack of use.

If a card account had no activity for long time , and is not linked to any other active account, I would call Amex before trying to charge anything.

If you hold two different IEC accounts (means different account numbers, the green is not a free supplemantary card in your name) , both accounts are linked and it should not be a problem to use the inactive card.

This probably isn't the timeframe you were thinking of, but I got an IEC back in March, sent to my US address. Last month I used it for the first time to buy a $50 helmet in Bermuda, and the charge went through. So they must've somehow noticed that I've used my US blue card a few times here already + a long-term travel note in my US blue account... still seemed like my purchase should've raised a red flag in their system though.