There are also the 3D resins. The type that are difficult to work are likely to outlast most of us from the look of it
But other resins I genuinely don't know.The reason why I ask is I have noticed that my unmade kits seem to be changing colour as they mature. Now I have bought (Some were given in with other things I had bought) some excellent cast resin parts, and one of these is a rather disscoloured footplate which has thin wire in the casting to keep its stiffness. It seems quite solid enough as resin goes. Resin can break if one drops a loco etc anyway, but there again, though plastic is a bit more forgiving, many a plastic model can break if dropped! At least resin is easily repaired! Not to say that one can't repair plastic.
But does anyone have any resin castings that are around 40 years old that are still going strong? Or have they become ultra brittle? Wondering how long these last?
A good thing about resin casting is that if one makes moulds, it is fairly easy to cast ones own things are very reasonable costs which makes modelling to a budget achievable if one goes down that route. Of course, one will need to first make prototypes to copy. If one ever tries making moulds, make sure any lightweight materials such as plastic or resin or wood etc is stuck down as I found by experience that lightweight parts one wants to copy can (And often do if not stuck down) float up to the surface of the rubber mould before it sets which is not what one wants to happen if making moulds like this.
I think my oldest kit is about fifteen years old as is the third loco kit that Smallbrook Studio came up with, and I had one of the first kits he made as I saw the photo in the Railway Modeller, fell into tears from the lovely look of the model it made and just had to buy it! It is absolutely fine. Had a few knocks and repairs when I chipped off the corner of the cab roof (Repaired using DAS modelling clay, though these days I often tend to file down resin offcut pieces into a dust and use that as filler which almost instantly becomes solid when one drops superglue on it. Of course one can simply put playdough around the area and cast resin into it and file or sand to the desired shape for the repair later. Many methods to tackle it compared to the size of the chip or damaged part, so as a workable repairable material, it is excellent! I was just wondering how long it lasts.