Flight levelx3 is a solid guideline to start with for track miles required. In my type (RJ) it is sometimes sensible to think about 4x height as a starting point, e.g. descending with a strong tailwind up yer bum giving a high groundspeed especially in icing conditions were lots of bleed air needs a higher floor for the flight idle setting.
Practical experience shows that when that 80 mile arc comes up on the ND then its 20 mins to landing.(give or take a couple). Our profile could typically be 300kts down to FL100, reducing to 250 by 8000 (A/C limit), 210 at 12nm, 170 to 4 DME, 120 at threshold.
Many permutations and fastballs possible of course but the answer always seems to be around 20 min for 80 track miles.