The Naim Hi Cap DR and XPS DR have been around 12 years, as the recommended service interval between 12 to 15 years, has anyone had one serviced or think that they can hear a need to have one done.
I think that your question is redundant, as - so far as I know - Naim no longer offer the DR upgrade, unless things have changed recently.
The OP’s question was regarding servicing.
The OP is asking about a service of an existing dr based psu.
If it ain’t broke, don’t fix it,
My non DR 252/300 was serviced after about 20 years. It still sounded great but I wanted peace of mind into retirement and associated reduced cash flow. I don’t think Naim changed the service intervals when they introduced DR. Belt and braces suggests 12-15 years but I was happy to stretch the envelope.