The RM night flights tend to only involve flying 2 sectors. Normally around 40mins turnaround. One BFS-EMA flight stays in EMA for 2-3hrs before returning to BFS (as far as I know) but that is it. Most flights will have you back at base by 1-2am.
If things go pear shaped with the fleet, you might end up flying a few more sectors in a night, but that is very rare.