In the current frontend implementation, pickup chats become more or less inaccessible after the pickup is over. They can still be accessed and replied to by clicking the link in the notification email though.
From my point of view, they should stay accessible a few days after the pickup, then get locked and vanish a few weeks later. How does that sound?
Pickup chat messages have the same kind of notifications as group wall messages (emails, app push and browser push). As the app is not very public yet and browser push is hidden at the bottom of the user settings page, it’s likely that it will take a while until the feature gets used.
Maybe the pickup chat should open automatically when you join a pickup that has already other collectors?