Can evidence you are not the debtor be deemed "too old" after a certain period of time? From the DVLA

No

Enforcement regulations do not require debtors to be "too old" to be subject to enforcement.

A debtor must only be older than 16.^[1]

Regulations do offer some degree of protection for debtors who are vulnerable.^[2]

Bailiffs cannot take control of goods or equipment required for the care of a person over 65.^[3]

^{[1] Regulation 2 of the Taking Control of Goods Regulations 2013
[2] Bailiffs and Vulnerable people
[3] Regulation 4(b)(ix)(cc) of the Taking Control of Goods Regulations 2013}