Happiness to a martini-drinker is a new bottle of Dolin. As I mentioned on the recent Bollinger article it was actually the Dolin team who showed me the codes printed on bottles and their meaning. The code in the image below shows that this bottle was bottled on the 331st day of 2019. I’ve never really found an old bottle of Dolin for sale however as they seem to be opened and consumed well before that. What I would say is always keep any vermouth in the fridge and ideally use up within a few months of opening — the primary quality of Dolin particularly is its fresh alpine aromatics. Opening a bottle should be as intensely aromatic as opening a fresh pack of coffee.
On the subject of refrigeration too — after I once heard a noted bartender talk out against an olive in a martini (calling it a heat bomb and therefore I guess therefore against the bracing nature of the ideal form of the drink) I check this concern by refrigerating my olives.