I haven't advanced too far yet- of the 4 garrisons I can do, at max time (2 to 4 hours) I recieved 7,7, 12, 12 mushrooms. in chat, others were talking about the "marsh" and "volcano" garrisons. the volcono is 12 hours max, and gave most people 24 mushrooms, although at least 1 person said they only got 12. The "marsh" was also reporting 12 or 24 on max time (I didn't hear how long that was). So, using your 5 free garrisons a day, you should be able to get from 60 to 120 mushrooms a day. If you are buying extra garrisons, 3 - 4hour garrisons for 12 each beats 1-12 hour garrison for 24.