How large is he? I know that large rabbits (i.e. Flemmies) tend to live a bit shorter than smaller rabbits. However, the age of life expectancy for rabbits has changed a lot in the last few years! People used to say 5-6 (what they said to me when I was a kid and had a french lop), but now it is common for buns to live many years longer. Once they are 6 years old, they are usually considered senior citizens. So it would be normal for him to sleep a bit more and be a bit more laid back. Obviously if there is a large and sudden change in behavior it would be a cause for concern, but if the vet says he is doing well I would worry less!
I’m sorry I can’t help you out on the age of my childhood lop, we had to adopt him to another family because we moved internationally. He was about 5 at the time and still very spritely.
Edit: I looked up more about french lops, and I think I was misinformed as a kid about what kind I had. French lops look like they are 10-13lbs? Mine was about 8lbs.
Anyone else have experience with these wonderful buns?