I was in your position many years ago in my mid 30s, and having been offered a 777 job at BA ultimately decided not to take it.
As has been highlighted seniority is everything at BA. Because of your age you will never get anywhere near the top of a long haul seniority list. If for example you took a long haul command when it came up you would probably be retiring no where near the top of the fleet seniority. Short haul may offer better progression but if that’s what you want the left hand seat at EasyJet and part time options later in life are not bad.
I’m sure the BA guys can give some better estimates for time to long haul command and the relevance of seniority on bidding and its impact on life style etc.