I remember a time when you could expect SAs in high end dept stores to be snooty. Thankfully times seem to have changed.
Yesterday I was at NM and I stopped by the Armani cosmetics section. I told the SA that I had purchased some foundation not long ago (about $70) and now my lifestyle has changed (not working) so I'm not using it often. I was asking about the shelf life.
He (and other SA who was also present) was so friendly. He said it should last a couple of years (pump bottle) and gave me his card in case I had a problem.
They were actually friendlier than some of the SAs at Nordies (who is known for CS)