It can be funny what we do and do not remember. When I was 17 I worked at Wendy's and we had a semi-regular customer who came in and I still remember his face and his order: A Bacon Cheeseburger with Mustard and Ketchup only, cooked rare. I can even picture his face and hear his accent. That was decades ago. Of course, I don't remember 99.9% of our customers. (He stuck out because he ordered the condiments in the reverse order of they way I had to communicate it to the sandwich maker, but he was never comfortable when I repeated it back as "Ketchup and Mustard only." He also liked the meat very rare. Very rare.)
For the most part, as shoppers, if we don't frequent a place all that often and we don't do anything interesting, we'll simply become a foggy, at best, memory to the retailer within a week. There is a store, for instance, that I shop frequently that has a rotation of 6 days. I've had the same cashier and return associate three weeks in a row before and I am certain that they did not remember me.
Of course, when you have a good salesperson on a more intense interaction (new homes, car sales), they will remember you for a long time. Thus, once you shop a new home salesperson, you can never shop that same person again. I was recognized at an apartment shop once my a leasing agent whom I had shopped 18 months before that visit.
Hard work builds character and homework is good for your soul.