There may be some truth to it, but if there is I think it's a very small factor as far as search engines are concerned.
I think the only value comes from what others think.
Part of the Google patent does mention consideration of how long a domain is registered for. The idea is that if a domain is only registered for one year, then it may be a spammer that is going to put junk on the domain and then dump it. Those that pay for more than one year should be more "serious". When word of the patent went out, there was a number of people that renewed for 5 or 10 years. Some registrars will let you register of as much as 100 years, which I think is insane.
The problem is that while the IDEA of considering registration length could be used, it doesn't that Google actually DOES. If I wanted to keep SEOs guessing, I would put all kinds of things into my patent and then not use all of it. And just because someone registers a domain for several years it doesn't mean they will continue to own it or keep the same site on it. If domain age is going to be considered, then than a SE can check the whois for the creation date and determine how long the domain has been owned by the current owner. Also, if I ran a search enigne I would keep a record of the domain like DomainTools.com does and know when the domain was first registered, if it ever expired, how many owners it had, and other information that may indicate how it has been used.
Whois Record
Domain Name: nielsentech.com
Registrar: Spot Domain LLC
Expiration Date: 2007-10-28 07:53:53
Creation Date: 1999-10-28 07:53:54
If domain age has any benefit, you think my domain would have better PR than zero...!
So, unless someone has some evidence of domain age having any "real" value, I think it should just be consided that the buyer will see some value to it.