I'm not sure whether it is intentional or not, but after I have unlocked all summons, completed the main story and now doing side quests I noticed I didn't have my summons anymore and I had to walk up to Mr slave, jesus, Tuong Lu Kim and Mr. Hankey and speak to them again and I get an achievement that says "Summon unlocked!" just like after completing the original quests to unlock them the first time. I don't get it. Are you meant to go back to each person daily, just to be able to summon them again or is this a bug? It's pretty annoying.