I have a senior card and find it very convenient even though I am just a sporadic NYC visitor.

Have never tried using it for Airtrain. One of my little Airtrain secrets that I will bury deeply in this thread is that the 6 month expiration date for the 10 ride card has never been enforced on any card I bought! If that's true in general, it might well be a viable alternative until too many folks figure it out.