I usually try to do three. It takes some work and attention not to be made as a mystery shopper. I try to select two short and one long. After my second shop, I exit the same entrance, move my car to the other entrance and come through that one.
I usually spend an hour which includes walking through the entire store and looking at clearance. I have purchased a hard suit case for 75% off regular price, a sound bar, blue tooth speaker and more. I like being able to have nice things at the fraction of the cost.
Do not read so much, look about you and think of what you see there.
Richard Feynman-- letter to Ashok Arora, 4 January 1967, published in Perfectly Reasonable Deviations from the Beaten Track (2005) p. 230