A good article on restocking https://thealexandrian.net/wordpress/48593/roleplaying-games/campaign-status-module-restocking-checklists

DM Angelo's easy method was to have multiple versions of the same adventure. So If we left and came back. Then he just ran one of those other versions.

My method is to have new gang bosses and a few new or renovated rooms. The players old map will mostly match up.

Once to just have fun with them. I had the main entrance sealed in while they were away. Some Holy Knights came by and decided to seal up the main entrance real good. The players remembered hearing about other entrances from captives while down there the last time. So this forced wilderness exploration to find new entrances.