Avios will last from 3 year of your last transaction. You can go to ba.com to purchase additional 100 Avios for a small cost and that will keep ALL your Avios valid for another 3 years when you might be able to go on holiday. A supply a Avios is always useful if you have to take a one way flight somewhere at very short notice in an emergency.

Alternatively, you can buy a flight for a parent, relative or friend as a thank you gesture. You do not have to receive payment (why are people so mercenary) and you do not have to fly with them. There will be taxes, fees and fuel surcharges to cover.

Just do not let the miles expire unnecessarily