Once you get used to an easy job, it might take you longer time to get back to competitve job evironment. My last job was super easy. Basically my work schedule was like this:
Arriving in the office -> Playing games -> Lunch -> Going home.
That's what we did all day. When I first came to my current job, I found my programming skill was not as sharp as before and it took my awhile to get back and be familiar to all th coding again.
I regretted that I wasted my 2 years there (my first 2 years was okay, I did learn stuff there).
I am just telling you my experience. However, I do suggest you to keep this job for awhile because you can use the time to focus on study and learn to get familiar with SAP. Learn to deal with different people even with people with less accounting knowledge.