I second the idea of riding off-road. Weather isn't as much of a concern and it's fun and different. I'm 65 and a normal road ride for me starts at about 65 miles, 5 miles is barely a warm-up. Off-road trail riding and 10 miles can be enough, depending on terrain. When road riding gets old there's nothing like a fun mountain bike ride to make things fun again.
I definitely need my rest days, too.