I don't like to have silhouettes instead of people on the back, and that buildings related to the current institutions are featured on so many designs

These are a current necessities, but nothing to sanctuarize for the future. The only thing that should remain stable in Europe are ideas, and the Swiss got it better on their notes

> These are a current necessities, but nothing to sanctuarize for the future.

Although the ECB does not today "withdraw" notes in the sense that they cease to be valid for most purposes, it does deliberately destroy old notes and issue new ones with different images to replace them, so the original series must be getting pretty rare by now - not rare enough to be worth serious collectors paying money for it, but your ten year old may never have seen an actual old Euro €500 note even though in principle those still are valid money in the Eurozone.