Do I need to disconnect motors from ESC's when flashing them?

I've just finished my 250 FPV build (built a quad before, which I've used much of for this build). 
I'm like well out of date on firmware etc. I've got Naze 32 (on baseflight) so I'm going to go to cleanflight (dont think I'm ready for betaflight yet). 

My ESC's are AFRO 12A's on their original simonk, I'm thinking of putting BHeli on them. 

would be somewhat inconvenient to disconnect the motors, but if that's what has to be done to be safe then that's what I'll do.

No need to disconnect motors as long as you flash correctly.
But.... flash wrong firmware and there's a chance that if the ESC goes up in smoke it can take the motors with it .
Do I disconnect motors? Absolutely not

Also remember to remove your props when doing that!