Slow down as you get older?, nope although I've had to invest in some prescription cycling specs & also bought some light armour after watching one of the younger ones (30 something) of our group go down hard. Probably riding as fast as I ever have at least on the downhill bits.
Our little band of brothers average age 50 still belt down the hills like nutters....however, I have been making thrice weekly visits to the surgery since mid June to heal a rather nasty wound and the other night when I was out, I definately felt myself braking earlier than normal. I'm sure when I've forgotten the pain in a few weeks, I'll be back to normal though!