Mimik, Beaucastel from a great year like 1990 can improve for 30 or 40 years, providing proper provenance. Mine have been in my cellar since release.
Old guy, mine showed no hint of bricking or tiring. I know I have at least one more and I will not be in a hurry to open it.
May you be in good shape when it reaches it "peak". Of course, "peak" is hugely subjective because these are such long-lived wines that there is plenty of room for preferences as they evolve. I recall drinking a mid-tier CdP at 55 and 56 years of age that was remarkably vibrant for a while ('a '53 consumed in '08 and '09) that cemented my opinion of the ageability of these wines.
Consume these whenever you want, although I would avoid Château de Beaucastel from ages ~8 to 15-20.