I want to change my store back to Nook N' Go. How long does it usually take for that to happen?
Once every month Nook will ask you what you look for in a store, and your answer can change the store. If you choose "variety" then you'll get/keep Nookington's, "hours" will get you Nook 'n Go, and "balance" will get you Nookway. This survey period will last a week so that all of your characters can vote, and then after that any changes will be made.
I couldn't survive without Nookington's so I'm never changing it.