PtF's comment made me go look at Hilton myself, as it's my only other program of note. Looks like they reserve the right to terminate membership and forfeit points after just 12 months of inactivity and that the 5 years is at their discretion! Yikes! (But aware I'm off topic)

Bringing it back to BA, I was surprised to read that Lifetime TP is a comparatively recent thing (2013?) and presumably therefore so is LTG?

Edit - yes, seems LTG was launched at the same time, presumably a number of FT members qualified on Day 1