Should? I'm not so sure I'd ascribe to "should make adjustments for age". One's practice evolves. That evolution rests on a continuum with safety at one end and efficacy at the other.
One may explore as they see fit. To do so aggressively, mindlessly, or carelessly vectors that person toward injury. But as long as their eyes are wide open about the prospects I see no reason to avoid.
That said, yoga provides the consistent practitioner with an ability to take what comes along in life with grace and an unfocused mind. When you can do sirsasana, the yogi minds accepts this without ado. When you cannot (and have done what you can to do it) then the yogi mind accepts this without ado as well.