Membership Rewards points do not expire if you hold one card that is linked to the rewards account. You could keep your points at American Express with a free Blue Business Plus card, and transfer them when needed.
If you do transfer them to an airline review this thread to understand the expiration policy of various programs, and then pay attention because the policies do change:
https://www.flyertalk.com/forum/mile...nt-expire.html
I do not think we can advise you on which airlines to consider without knowing your home airport and typical destinations.
Not interested in sticking with AMEX. I checked Air Canada, but they do not seem to have many non-stop flights to Europe. Home AP would be Newark. Open to any suggestions.