I thought I read he filmed a crapload in advance. Will be weird seeing him on screen for years to come if it is true.

Edit: Okay, what I read is already old news from April https://www.syfy.com/syfywire/stan-lee-more-marvel-movie-cameos , so it had referenced Ant-Man and Wasp plus Infinity War, which already has come and gone, but now he does have the second part to Avengers as well as Captain Marvel. I would love to see him one last time in the next Spider-Man too, I wonder if that was filmed.