I disagree. That would depend how you implemented it. It's not impossible to check if a token has passed its timespan, and if it has, it would and should be considered invalid. .TokenLifespan = TimeSpan.FromHours(6); You also won't be able to write the logic for the later without a tokenlifespan being set.
Doing the research shows many implementations when searching c# using "TokenLifespan" to check if token expired online.