if a member can stay out of the forum for over 5 years, what will be the probability that they will come back to the forum someday
May I remind you of this thread
Is laszlo back? by fillippone. The probability is as equal as Laszlo a legendary member of the forum acting his account again after several years of being inactive. So there is a possibility that someone who has left the forum for long can come back.
I understand the DT system to work with trust and reputation of a user in the forum that makes other DT members to include them in their trust list and even though some users earn trust due to the assessment of their past behaviors to their present but i think that an inactive DT member should be removed
The DT system is different from any other thing in the forum, a valid accusation and a valid feedback sticks of the profile for everyone, if DTs who left are removed the feedbacks will also change sharp.
In my opinion it's nothing to worry about because it still serves it's purpose whether they are active or not. If you had referred to there thing in the forum that inactive members occupied it would make more sense.