As said before dogs w/ floppy ears tend to get dirtier faster. My rott has to have her ears cleaned out a few times a month in the summer as she is always swimming & playing in the dirt, plus the humidity does not help. My husky mixes only need theirs cleaned out once a month & they are not even dirty. I check my dogs over once a week.

A few pointers for the future, especially for floppy eared dogs: Clean ears w/ a cleaner that contains a drying agent in it.
Clean the ears after bathing & swimming
When the dog is just lying down flip the ear so that the air can get to it
Sometimes in between cleanings just a dry swipe with a tissue can help