How do we know, the fuel penalty/burn rate, with the LE devices extended? This is an important factor to decide whether to hold, or divert.
I've never flown the 737 but if I wanted to know the fuel burn rate I'd take a look at the fuel flow gauges, especially if the aircraft configuration was not normal.
Then, if there was a question of range and/or endurance, I'd do a few calculations involving time/speed/distance. Back in my day they used to call it navigation.