I have a question which I couldn't readily find via a list search.

When a maker sells a product of a specific age (e.g. 10, 15, 18 yo), rather than to a taste profile, are these products always released annually? For example, when PVW 15 is bottled at a given time, is there always another set of 15yo barrels coming up for bottling the next year? From various threads, I've inferred that this is the case, I was wondering if intervals other than a single year are ever used, either less or more. I suppose in case of disasters (fires, etc), there would be gaps in availability due to having to start from scratch, but I'm referring to normal circumstances.

Thanks, and sorry if this had been discussed before.