He could be at rest somewhere, reminiscing about the age that was lost to him.
That seems to be what people expected he would do. With Hakkon long dead and Corypheus now defeated, with the Inquisition itself only picking up the remnants of trouble, there is no desperate need for the old Inquisitor's weakened help; he has no reason to keep going. The Inquisition would provide for him if he wanted to retreat to somewhere safe and comfortable, wherever that might be. He had been promised as much. Retirement, much overdue.
Ameridan has slowed down considerably, compared to the pace at which he did just anything before he trapped himself in time with Hakkon. He fights no dragons, storms no castles and holds no lines against darkspawn or demons. He has attended very few banquets or balls and participated not at all in political scheming. When he travels—with the current Inquisitor, or on his own—it's never very far from Skyhold, and with the understanding among his companions he is not as fast as they could be, that he needs more frequent stops, that weather and terrain affects him more than it does others.
Still, he presses on. He won't stop. If he does, he's certain he will never move again.
Traveling with Cathal is... aggravating, at times. He's not yet decided if it is envy for that endless energy (what a foolish thing for the old to be envious of the young, but he would hardly be the first) or anger for the carelessness of risking one's health like that, or worry. Cathal, he's decided, must be too young for aching knees and stiff shoulders, but they will find him soon, by the time it is too late to prevent them. Maybe that is inevitable. The young never listen to the old. They'd never get anything done if they did.
Can't you speak to him? Cassandra asked him back at camp. Surely he will listen to you.
Ameridan doubted him, but went, because despite himself he was worried. Now he stands beneath the tree Cathal has climbed into, arms folded across his chest, more annoyed that he's been sent here as though to retrieve a misbehaving child than truly anything Cathal is doing.
Until Cathal speaks, that is, and his frown deepens. Does he think he is dying? Does he have cause to think so? Ameridan would ask, but he doubts he'd get an answer.
"If you think sitting in a tree is worthwhile, I suppose you may", he says instead, pretending he never noticed the dire prediction. "But you are making your companions worry, and that helps us none."