Low fuel emergency in DFW

One guesstimation regarding how quickly a runway can be cleared for a
landing in the opposite direction. It's not uncommon to have three airplanes
on the departure runway - one accelerating, one taxiing into position at the
end and another (the next for take-off) taxiing into position at an
intersection. Allow 1 minute for the take-off run and another for initial
climbout. As for the other two airplanes, behind them is typically the
departure queue blocking the quickest exit, so they will need to taxi on the
runway to the next free exit before vacating the runway. That probably takes
the same 2 minutes. So 2 minutes minimum. Then consider the wake turbulence,
if it was a heavy taking off - do you really want to land into the wake?
That might cause an emergency all by itself. Just my $0.02.