When the Pokemon in Dream World disappear.

[Canvis the Smeargle]

There are always Pokémon at the start of your Dream World run for the day. Eventually, though, Pokémon and items disappear completely from the zone, and each slide you can visit is empty. Recently for me, Pokémon and items already disappear 10 minutes before closing-time (the end of my hour). Sometimes 20 or 30 minutes early instead. I fully explore the zones each time I visit and I never cut my journey short while I'm halfway through, so if it has something to do with returning home too early, I don't think that's it. It's strange even if it sounds like it may happen because my hour is almost up. Strange since I've been able to explore until the last minute before. Why do Dream World Pokémon disappear and when?

[Joeno]

There's a limited amount of runs through the zone. I believe that after you go through ten times, no more Pokemon and items appear.