A transfer of Avios from BAEC to Iberia Plus will not extend the expiration of your Iberia Plus Avios. A transfer of Amex Membership Rewards or Chase Ultimate Rewards points will.

Your ability to earn IB Plus Avios via various methods might depend on your country of residence. Here's what I'm seeing here in the U.S.:

https://www.iberia.com/us/iberiaplus...ure-purchases/

Note that, depending on the particular redemption you have in mind, Finnair or Qatar Avios might provide better value than BA or IB Avios. Avios in a BAEC account can be transferred to a Finnair Plus account, or "linked" to a Qatar Airways Privilege Club account for redemption.