I had some pepper seeds sprouting after 19-20 days, from a pkt purchased from a reputable seed vendor, when most of the peppers sprouted on 8-10 day.
Although I do find 20 days a bit too long for a pepper to sprout, and if nothing shows up after 12-15 days, I re-seed.
I do use some heating to keep the mix warm, so it is not the cool soil that causes long germination time. I guess some seeds might be a bit old
