I agree that it's not beneficial for BA from a financial point.
As a Marketer... The only problem with Lifetime TP is that 25k to Lifetime Gold is for a lot of people a very far goal and hence not desirable.
Maybe Lifetime Silver would be an interesting intermediary to give people an incentive for the 'extra' TP. Especially because I can imagine there's a lot of people (not FT'ers, ha) that are constantly between 600 and 1500. I do believe it's a pretty big gap for 'ok' additional benefits.