I always like to keep a minimum of 200k plus a 241 sitting in the household account which equates to a J return for 2 anywhere on the BA network. Its always nice to have that sitting there in case we want to book a last minute trip.

I never let the balance build up too high though because the value of an avios will never appreciate. I've been stung too many times by hotel schemes when they de-value overnight whilst I'm sitting on a huge stockpile. So I think 500k is the highest my BA account has ever gone.