Board Thread:General Discussion/@comment-12330013-20160101022123/@comment-24577221-20160216040621

Each monster brings back one "random" item per trip. So if you send 1-element monsters in 8 times, at 1 hour per trip, instead of a 4-element monster once for 8 hours, you get 7 more of those items. Also, since the probabilities of getting slime, mushrooms, and peppers are capped at 100%, the statistical average yield of those items is higher for lots of short trips than for one long trip with the same total time (see the Wondermine Strategy section). The downside is that you have to be playing the game all the time to keep sending your monsters in over and over.