Using 3s one day 4s the another

Say your running your quad on 5000 mah 4s lipo. All of your batteries are depleted and need to be charged. Except for the 5000mah 3s lipo which is fully charged. Is it feasible to go into MP or APM planner and simply adjusting your voltage settings to be for a 3s lipo so you can get that extra flight in. Assuming props are sufficient for the 3s lipo. Has anyone done this. Any problems.

I used to have just the ma battery failsafe setting set as I used to use 3s and 4s batteries both of which were 5000mah. I never have telemetry connected when I fly so it was the easiest way to do it.

Worked fine, though the quad was a lot more sedate on 3s so these day’s I just stick to the 4s.