Brake fluid recommendations? Dot 3 VS dot 5

When we bought dad's cuda in 2012 it had Dot 3. Peeled paint under the hood. We swapped to Dot 5. And when I say swapped, I mean we simply bled Dot 3 out and kept topping up with 5. Kept bleeding till we saw purple at all 4 corners.
That was 13 yrs ago.
I agree. I have done the same on old system's.
Funny thing is some don't know.
Starring with farthest line from the master (Longest) I have seen many who don't know that's how to do it.