Maybe it's not a big issue but i think dt members should be always active as their feedbacks is publicy shown and may need updates.
DT members aren't obliged to 'be always active' in any form or way. Most feedback is left with a valid reason and shouldn't need to be revised that often either.
Your opinion is extreme. Feedback with a valid reason can also be revised and changed and even removed. If new evidences revealed, then feedbacks should also be appropriate. Let's take the case of TMAN's feedback on BestChange profile, the case has been resolved and all other feedbacks from other users has been changed from negative to neutrel except the one from TMAN which is still negative and publicly shown in red in the BestChange company official profile.
As your feedback can be shown on others profiles, and as you are the only one who can change/remove it, you should always be responsible by being active or ask to be removed from DT lists if you are planning for a medium/long term inactivity.
I recall seeing other proposals for expiration of feedback, or maybe negatives convert to neutrals, but surely there might be some cases, like you mentioned, in which a member might need to reconsider feedback that s/he has given.
As a policy consideration, it seems more difficult to actually require that a member has to do something (such as reconsider feedback that he gave) based on his/her having had already done something...even though that negative would end up showing up forever on an account (or situation) that the vast majority (or even everyone else) had decided to remove or to change their feedback.