I tried this. Older workers are great if you have a stable problem (better than young workers on average), but are terrible if the job requires a lot of context shifting. Startups and stable problems are rarely found in the same room.
I find it easier to do now than I did when I was younger, I see it as just what the job is. When I was younger, a sudden demand to do something different would have me annoyed because it was distracting me from what I really wanted to be working on.
Now I know that everything will be different in 5 or 10 years, so it doesn't really matter what I'm working on as it will be irrelevant soon.
My job requires a ton of rapid context switching, but I do find it much harder now than when I was younger (I am 46).