OD, it sounds easy, but it all depends on the situation.
Factors
Final approach speed
Company SOP's (when do they want you to be fully configured, mostly 1000 or 500 ft)
Wind, possible turbulence etc etc etc
Surrounding terrain
I've turned onto the localizer clean at 9 miles with ATC asking high speed (210 kts at that stage) with 40 kts headwind and was fully configured, landing checks done at 1000 ft. I've also had to take gear at 15 miles because of a stonking 25 kt tailwind and the plane actually speeding up when I wanted it to slow down.
In general, the 737 is not very good in going down and slowing down, i.e. losing energy. The speedbrake is not very helpful once you get below 220 - 210 kts. I.e. a tailwind on approach is always interesting in the 737. You can never be ashamed for being configured at 1500 ft. A lot better then a G/A due to unstability of the appch.
If in doubt, forget about the 5 secs you win and configure early!