When you initially start the game, you are forced to click the properties you own to generate revenue. With the purchase of a CEO, this process becomes automatic. That is, the CEO will operate the property - that is, the CEO will click the property for you. However, the CEO isn't perfect, and as such has some idle time between ticks. The delay between clicks depends on the level of the CEO.
On the Game Help page in the CEO paragraph it says the following: however the CEO will never be perfect, so you can still manually click on properties to make them run faster, This is true, however on certain levels you won't notice it anymore because of the speed increases you will gain through achievements.
The formula used for the CEO idle time is Investment-Time / CEO level. Lets say a Gas royalties without achievements for speed increase takes 2 seconds to complete. If your CEO is level 1 this means the property will run, then it waits 2 seconds and it will run again.
A few examples for the first 10 levels of the CEO.
In the examples the investments have no speedbonus.
The idle time is based on the investment time after speedbonusses and not base time.
While I was writing this I wasn't sure but finding out that a level 16 Saudi Field CEO should have an idle time of 2.5 minutes I can say for sure that my CEO isn't idle that long.