Hey Tummyache. I've had an endo + colonoscopy on the same day twice and both times things went well. Both my colon was clear and endo normal and the procedure took 25 minutes the first time 35 or so the second. Hope that helps.
It isn't uncommon to have both procedures done on the same day when they are either diagnosing or checking the progress of IBD or other disorders.
My son had his done under anaesthetic. He was at the surgery for about 2 hours all up with the procedure itself taking about an hour. He had no issues afterwards.
If you have an anaesthetic you will not be allowed to drive yourself home.