How long does it take for a tan to fully show up after using a tanning bed?

I have been going to a tanning salon for the past 3 days now. The first day I went in a standing one for 5 minutes (I saw no results), the next day I went in it again for 8 minutes (I had a slight tan line), and the next day I went in a laying down one for 8 minutes (I got a little red, but a little tan too) So how long do I need to keep going to get a full tan? Also, which bed should I use or should I just alternate? Thanks! ps. I know the risks for cancer and everything so save your breath.