You need one side (cool side) 80-85 degrees and the other side (warm side) 90-95 degrees for the ball and 88-90 warm and 78-80 cool/ambient. There is NO need for the temperatures to go down EVER, not even at night if your not breeding.
Just because a reptile store is all about reptiles, doesn't mean the employees that are hired know or have experience with reptiles.
That ladies advice would allow the snake to SURVIVE. You want your snake to THRIVE.