(Note: If this takes more than $1,000,000 to implement, please ignore!)
If it will help the flow of conversation why not
Newbies so often start threads and then abandon their account when conversations do not go their way. Then other newbies come along and reply to the OP that hasn't been online for weeks.
There are discussions where the Original Poster doesn't need to be online during the flow of the discussion in the case of a boxing event one can open a discussion about two fighters fighting for a World title, and there are two months before the fight, the discussion will continue and everyone can provide updates
It would be nice to have a notice near the name if the user has not logged in a while. i.e: (Inactive for 6 days). Could just be for newbies, or for every topic starter.
The warning "This post is xx days old!" does not address this issue.
If the OP opened a thread about his issue or complaints, which is considered a personal issue, then this is an instance where we need this feature.