Yes, and no there is no service interval for them. Typically the nylon pads last around 100K, and they're the primary cause of catastrophic engine failure in the D2. I've seen failures from as little as 120k but my Murple is on the originals at 320k so ymmv, literally. At the very latest I would do them with the second timing belt.
Its a good half-day's work with the engine in after the front end and timing gear is off. Allow a day if you're not taking the front end off. Itsa two person job to get the inlet cams back in - one to hold the tensioner and one to slot the cam back in place.
These are the nylon pads:
https://www.ebay.co.uk/itm/4x-Pad-Ti...K/252466154290
You also need 2x 077198217 which are the gaskets for the tensioners. I recommend removing the little gauze filter from the tensioner when it comes off as that is the primary cause of tensioner failure.
Have a read of Big Red's and Stephen's FE WITW threads - there's a chunk more detail on the job in those
