I usually leave my old pump site in for about an hour after I start my new site.
Last night I fell asleep and forgot to remove my old site.
Took it out this a.m. and very red, raised, and inflammed. It is never this way when I pull out after an hour. Tonight it still is very red and like a scab, something I have never had before.
Warning: do not leave site in over night after you are no longer dripping insulin in via the pump.