Other than price checking and general availability I don't think a tremendous amount of research is done. I wouldn't say none is done though; just a very small amount. I wouldn't say it's a tremendously popular impulse item either but more of a necessity every so many Months.
It's a universally recognizable brand with a tremendous amount of competition which means I've had to slug it out with some of the national level chain stores on occassion. That said, I've still done very well. Some of the bigger stores don't have the flexibility in their systems to sell this product the 'right' way and so they can be had in a competitive market place like a shopping comparison engine.