I'm getting ready to install a JDM F22 to replace my original after it ate a valve. I'm going to give it a new water pump and belts of course, and since the new-to-me engine is ~30 years old I figure that the rubber seals will have aged enough to warrant replacing before they leak while inside the car. Now you can find Honda brand seals new-in-box on Ebay, but how old are they? Are they all leftover stock from the late '90s?

 

Hard to say these days if someone is selling NiB Old Stock or if it is all new stock. Probably best to pose this question to the eBay retailer.

I would say that some of these kits have been sitting on the shelf for a while. As long as they have been stored properly they should be good to go. It's not like they are like the old dry cork gaskets. Most of the 90's Honda stuff is good quality poly, paper fibre or metal.

 

I have wondered this too, I have noticed new part bags have QR codes on them. Unsure when that come in or if it applies to all parts but that is something.