I think 34/35 is when I began to notice actual age related differences - relatively small things like not being able to take it for granted that your sore back will be good tomorrow and I'd accrued enough general injuries over time that they were noticeable and compounding - sore/weak knee from a car accident, stiff shoulder from a motorcycle crash, etc.
When you're 35, 35 feels pretty old compared to the personal status quo.