I don’t think the season tabs should disappear, especially if you completed their challenges. Having those completed were the only season exclusive reward for the first season. The grind to get them all was horrible, and removing them would be a slap to the face to those who actually completed them. Because really, no one did them for the Commendation Chests they rewarded. 600 weave runs for 15 Commendation Chests? Laughable.
Instead of simply removing them, there should be some indicator that they can’t be progressed on (if there isn’t already, I don’t know what those challenges look like for people who failed to complete them). Like how the completed challenges have a banner saying “Reward Claimed”, these challenges could have a banner saying “Expired” if you did not complete them.