I used to be head of a department and having to get shopping in the lunch time, yet also setting an example by not being late back to work. Now I am retired I avoid shopping at that time and on saturdays too. Do go on the local open air market which is a different thing . There I feel I am helping local small business to survive, can buy small special items that you would not get in a supermarket. As I have a bad back and often do not sleep well on the contary I can visit the supermarket at about 6 am. It suits me, quiet time to shop so in and out and job done early, especially holiday time when I will be home before the rush of shoppers. I am suiting myself but also being fair to other shoppers. I have on occasions , when the person is spending such a long time at the checkout, asked quite politely if they intend to be long as my back is painful and I am unable to stand long. I will therefore have to leave the shopping as cannot wait any longer. Usually works, as it is totally true, the staff do not want to have to replace the goods but cannot say well put it all back first and the person talking cannot say anything much and will usually get on with paying