I've got experience using these vacuum pumps with a chamber to purge oils. What they are saying is that because you are creating a vacuum, the oils involved will become gaseous and get mixed in with the oil. So what they are talking about is using the pump/chamber excessively, purging a lot of oil gunking up the oil resulting in the resin collecting on the plastic parts of the pump and eventually ceasing the pump due to the resistance from the oil.
Also, when there is dirty oil, the pump tends to not want to work as long without a break to cool off. I run it as long as possible because when the vacuum pump is on, maintaining the vacuum, you have to have the vent valve slightly open so the pressure is consistent. After many years I can say that you will extract the oils faster the longer you do it with the pump on, but you need a good one to run 24hrs, even 6 hrs. Metal internal parts reduce this and can easily be cleaned using any kind of ISO while changing the oil. They want you to change the oil after every use, which can be expensive, but allow you to run the pump longer b4 it overheats. Watch the exhaust, when/if it gets cloudy or smokey or you smell smoke, turn it off, but get the pressure locked in cause you may not be able to turn on a hot vac until about 30-45mins sometimes, seems to be a safety feature.
Just change the oil as you have extracted oils for say 12-24 hours. You will be happy with the longer life, run time and overall performance of your pump.
But, when the pump is on, maintaining a specific pressure, the extraction of oils will be faster. You will notice right away that the bubbles will slow down dramatically after the pump is turned off and it's still under vacuum. So, try to run it as much as possible, get your money's worth out of that oil your gonna be replacing anyway. You can cut times in half, 4 times by running the pump and maintaining vacuum as opposed to getting it up to pressure and turning off the pump. I know this for a fact and have kept this in mind for many years now and have tried many times to reduce the pump use, but it just adds time to the extraction process when off. I only run it 30min, turn off, let sit til cooled and another 30 min. At first, I may run it for an hour, all depends on the pump temperature and trying to avoid overheating.