Sorry, but carrying an extra 6 knots means sweet frick all! Over 15 min, with no other speed changes it is roughly 3/4 of a mile. If you were straight in, behind other traffic then things might tighten up but then good airmanship would have you using TCAS to judge the gap.
Otherwise, with several turns before final those 6 knots disappear in ATC vectoring and sequencing. Which is why there is a 5not or 10 knot 'window' in most IFR environments. It is also why ATC always says 'no problem' if you ask them to do 185 instead of 180.