Why does sedation take so long? I'm having an endoscopy done and was told by my GI doctor that my sedation will take about an hour, why is that?

Misunderstanding. Your GI was probably trying to tell you that the effects of the sedation will last an hour. It usually kicks in very quickly - usually no longer than a minute.
Endoscopy sedation. Perhaps he misspoke or u misunderstood him. Probably meant u would be sedated for about an hour during the procedure (not sure which endoscopy you're having). Inducing sedation for colonoscopy, for example, involves starting an IV & adding the sedative medication. Sedation comes very quickly for most people.