Your backup plan is to differentiate from younger developer.

I have defined my advantage should be experience, wisdom and maturity. I try to deliver something to my managers that they just can't get from a developer that is very bright but has just couple of years of experience. I try to spend more and more of my time learning and deliver with less time expenditure.

Also, don't get discouraged when you don't get a job somewhere because you are an older guy. You should be thankful that you did not get the job, probably it would be a dead end anyway.

You don't need every place to accept your age. You just need one -- one where you will feel at home and be happy offering your services.