Initially signature bounty was more worth the effort before the bounty campaign space became more saturated. It's still worth something in my opinion.
Depends on the campaign itself, allocation, number of participants, ranks and the actual value of the token when it comes to exchanges, promised end date of bounty must be fulfilled, why would they have to require participants to keep signatures for another 3 weeks if the bounty was finished, Base on my experience it just took 2 to 3 days prior from the end before removing because they have to count the post of the participants.