They are getting beat up like the Who. No Jerry. No Phil.
Don't be mistaken...this is not the Grateful Dead. Unlike other bands, when Jerry died, the Grateful Dead was over. Each member has gone on to do their own thing for the past 20+ years. Just so happens this band has 3 of the four surviving members. Minus Phil. Phil still plays, he just likes things a little different and prefers to do "residencies" at venues and stay off the road, avoiding travel days. But there has been many incarnations of Dead member projects with anywhere from one to four surviving members. None of them pretending to be something they are not --new members, new arrangements of songs, varying setlist formulas and so forth.
If getting older means being 'beat up' then so be it. Personally, I disagree.