Safety of spare parts supply (older models) – which manufacturer is the leader?

Hi, since I prefer to buy older vehicle models (which are usually not produced at the time of purchase) and drive them for quite a long time, I would be interested in which manufacturers here guarantee a safe spare parts supply over a very long period of time and which manufacturers here leave the (youngtimer) owners rather in the rain. At Opel I have had very good experiences in the past years, at Ford and VW rather less good. How do your experience look like? and where is it special?