I would throw this out from personal experience - career changes are MUCH easier the earlier you make them. Switching from teaching to engineering or coding at the age of 50 versus the age of 25 are two very different things.

Why would a company invest in a new 50 year old that has 10 to 15 years of work left in them, (5 of which will be learning the new job)? Sure, there are reasons why the 50 year old might be a better employee than the 25 year old but few companies, unless you know someone and are INVITED to apply, will take that risk.