I have a flight booked on TAP Portugal in a few days. They are part of the Star Alliance scheme covering over 20 airlines, some of which I might travel on over the next few years. Having looked at some of the TAP scheme, they give discounts off their flights, but some of the other benefits can only be taken if you live in Portugal, whereas I live in the UK. If you have one reward scheme, then you can travel on any of the member airlines and have points credited to that account. This means it might be worthwhile to join a frequent flyer scheme for this flight.
Does anyone know of which scheme might be best to join, some of the criteria I'm looking for are points that don't expire after 3 years such as with TAP, or being able to use points for an airport lounge even if flying with a non member airline, or gift vouchers to spend in UK shops.