Try to be holistic and rational here; take for a example, a certain scammer is discovered and tagged by a DT member in 2018, and down to 2025, you exclude the DT member that tagged the scammer due to inactive, don't you think the scammer will simply return to the forum to scam?
When someone leaves DT their feedback doesn't disappear. It still remains there. To form an opinion about a member, you should look at all trust feedback, not just DT ones. If someone attempts such a scam years later, it will be noticed quickly and other active DT members can also tag that scammer.
That is how it is supposed to be, but in reality, it doesn't play out that way. This is because users who are not in DT are always reluctant to leave feedback since their feedback won't be visible for the meantime. The majority of them that tries to do so do it as a form of retaliation which isn't always correct. This is the reason non DT feedbacks are becoming almost irrelevant in the forum.