Avios themselves do not have any expiry.

If you go 36 months without any activity in your account (essentially any earn or burn), then you will forfeit the balance in your account.

Two notes:
1. Transferring Avios between your accounts in the various schemes that use Avios (i.e. BAEC, Iberia Plus, Avios.com(Previously Airmiles UK)) does NOT count as activity.

2. If your BAEC account is part of a household BAEC account, and if a member of the household has status (not sure if that now includes the new Bronze tier, or just the historic Gold or Silver) then you do not need activity.


The above is about Avios. Do not confuse with Tier Points (which are also awarded from flying and are what are required for status), these are reset to zero at the end of your own personal membership year.