Im not sure if Don has false teeth maybe some work done but to me he sounds the most like he did in the early days. He has held onto that strained vocal sound since the Eagles began. I agree Glenn was at a peak during the 80s when his voice was so smooth on the soul numbers, but the power of his voice in the early years of the Eagles, when he dominated and belted out songs like Outlaw Man and Out of Control, noticeably diminished. I never felt his voice had the 'fullness' or 'body' it originally had and was much thinner. Just an opinion based on what I hear granted there are exceptions to that.
Timothy in in my ears is only now just losing that range but to have had it for so many decades I think is commendable after all as you grow older everything is going to decline including your throat and your vocal quality/range.
They kept a great standard for many years