The short answer: No
The longer version: Younger testers and younger developers are not more valuable than older testers and developers. The person who said that developers age badly is probably invested in having a lot of cheap labor available and willing to overwork themselves and who lack the experience to know when they are being asked to do something that's either not possible or not ethical.
Because this is such a damaging perception and gets repeated a lot, I'm going to go into some more details here.
The programmer is able to withstand two technology changes, and these changes are every four to five years. And then he has to go to other things.
Some of the highest paying IT jobs out there are for COBOL programmers. Why? Because there are millions upon millions of business applications written in the language that need ongoing maintenance. C and C++ programming is also highly paid, for much the same reason (as well as the operating systems written in those languages). Assembler falls into the same category.
On top of that, the language software is written in is secondary to the ability to define a problem space and logically structure a solution so that a computer can perform that solution. Some types of languages are more suited to some types of problems than others - I wouldn't want to use Assembler to code a web site and I wouldn't use HTML to code a back-end mainframe app.
Defining and solving a problem in a computer-friendly way is the most important skill a programmer possesses. That skill improves with practice no matter what language or technology set the programmer is using.
On the tester side, the most important skill is finding and reporting gaps between expectations and implementation, that is, working out what someone using an application will expect to happen, finding ways the application doesn't do what is expected, then communicating that information to someone in a position to change the application in a way that will convince them they need to change it. Everything else is secondary. And, like the most important skill of a programmer, it's something that improves with practice.
Older/Experienced Programmers are probably better at defining and solving problems. They're also more likely to know the best tools (languages) to use to build the solution. And more likely to be able to build a solution that's more robust and maintainable.
Older/Experienced Testers are probably better at finding and prioritizing gaps between user expectations and application behavior. They're also likely to be better at advocating for their findings.
Just because someone who prefers to pay less per person (and more in the long run) says old programmers or testers aren't worth as much as young ones doesn't make it true.