If at least half the letters in FAANG aren't blown away in that time period, it would suggest a tech environment so stagnant that it would be impossible to justify the compensation.
And lasting 30 years at a surviving FAANG company is such a low-probability prospect that it's not something reasonable to include in any future planning.
Very few FAANG engineers can actually expect this outcome.
EDIT: Removed shock word "preposterous", sorry about that.