I think you have to work on it being 10-12 years for LHS. Last year was abnormal and a large number got early commands on SH. I don't think it will be repeated like it was because all those new commands will have a 5 year freeze. Retirements are not in any significant number and the fleet growth is fairly flat over the next 4-5 years.
The grass is greener at BA it's just our brown patches are in different places. A friend of mine is a captain at a LOCO and he is happy with his deal. Yes there are issues which are different from BA but he earns a better salary and is home each night. He decided BA was not for him and he is probably right. As for me I have learnt the skill of ignorant bliss and I feel fortunate to fly for BA with all its rights and wrongs. If you take it back to basics the job that pays fairly/well or "market rate" and continues to do so is a good one.