While players enjoy the increased drop rate of mounts, the Collector’s Bounty event also comes with some side effects! It’s super easy to fill your inventory with boss loot, which is slightly annoying, especially when it boils down to tokens!
This is what your inventory will look like upon visiting Icecrown Citadel, but that’s still nothing compared to clearing Mythic Sepulcher…
When you finally solo Mythic Sepulcher, trust me, it’s not that easy as it looks, your inventory will look like this:
How to Avoid This?
Having a mount like 
Reins of the Grand Expedition Yak that comes with a vendor to whom you can easily sell all the boss loot to, is possibly, the easiest way around this.
If you don’t plan on investing into a mount that comes with a vendor, prepare for downtime. You will most likely need to visit a city or manually delete items, which is a real pain.