The oil in the pump doesn't need to be changed very often. I'd be more concerned if the oil level increases above the full mark as it would indicate that fuel is leaking into the pump. The oil will become diluted with fuel which provides for very little lubrication of the fine moving parts inside of the IP.
Yes, I had that problem and changed the oil in the IP. Then the car got taken apart for painting... 2 years later it's driving again. I guess it's time to get the big syringe and a plastic tube and suck the oil (or oil / gas) out of the pump and fill it again.... Hoping for more oil, less gas.
By the way, I got a syringe that is about 1" diameter and 5 inches long that a tube can be put over. I'm hoping that saves me a lot of time getting the oil out of the pump...