You only have 60 days from purchase to leave feedback.
Feedback is voluntary.
If you feel feedback is necessary but the deadline has passed, you can leave Responses to any feedback (your own or the seller's) indefinitely.
Responses don't make any difference to the recipient's FB score but the main purpose of FB is public relations.
And Responses really stand out on a page.
The most effective Response, like the most effective feedback, is calm and factual.