Replace those worn-out outlets!
This is not a question but more of a warning.
When we moved into our house, we noticed that many of the receptacle outlets were worn-out and that plugs would fall out very easily. I told my wife that this is not just a nuisance, but it is unsafe, so I replaced at least half of the outlets within the first couple of days. My wife thought that I was being paranoid and that replacing them could wait.
Just this morning, I was making some toast and I noticed a burning electrical smell, so I reached behind the toaster to unplug it and the plug was so hot that it burned my finger. The plug was toast! It was melted and black on one side. The outlet was also melted and black by one of the slots. I never thought about changing the appliance outlets because they looked like recently installed GFCI's. The one that burnt was a standard outlet that was on the load side of another GFCI. It was probably an older outlet that was reused when the GFCI's were installed.
All of these worn outlets were cheap residential-grade. The kind you can get at Home Depot or Lowe's for 49¢. I always use commercial-grade outlets. They might cost a little more, but IMO it's worth the extra expense.