Here's how I look at it:
An All Grain batch takes 8 hours.
minus 30 minutes if you have a good wort chiller (counterflow, for example)
minus 30-45 minutes for a single infusion mash (no additional heating and resting steps)
minus 30 minutes if I can clean up outside with a hose
minus 30 minutes if my carboy and other equipment is already sanitized, or if I can do it during the boil (such as maybe if I have a helper or have sanitized everything ahead of time)
Minus 40 minutes if you have a really good burner (speeds up the time-to-boil, strike/sparge water heats faster, etc).
Minus 10 minutes if you have a brew sculpture or dedicated setup that allows you not to have to move stuff around a lot.
Plus 10 minutes if you grind your own grain
Plus 5-10 minutes if you have to measure out your own ingredients
Plus 15 minutes if all of your brewing supplies aren't all kept in the same location near where you use them.