Im sure some sellers will sell bulbs that are past their ’due date’ but i dont think that includes any of the reputable sellers. did you get the bulbs off someone on EBay or similar?

bulbs should be sold the year they are harvested. youre right that some will last longer than others but unless you know how theyve been stored or can inspect first its kind of risky.

If your alliums feel firm and have some weight to them they might be fine. sometimes my onions last months, sometimes theyre sprouting and rotting after a couple weeks, so its kind of the saame thing.

Provided they are kept under ideal storage conditions - correct light, temperatures and humidity - at least 12 months, maybe longer. But almost impossible to duplicate this for a home gardener. If the bulbs are still hard and firm, not mushy/rotten or shriveled/desiccated, then they should be okay to plant. Might not bloom dependably their first year though.