Does total distance with buddy remain if you switch your buddy?
I have over 600 KM with my Snorlax buddy. I am thinking of switching to Lapras for Halloween. If I go back to my Snorlax will the 600 KM remain or will that get wiped to 0?
I kind of like seeing 600 KM with my buddy so not sure if I want to switch if I lose that.
Answers
Also adding my confirmation that I've switched back to a buddy and as long as it's the exact same pokemon it keeps the distance (switching to a different Snorlax will show 0km as it wasn't your buddy yet!).
I don't know about evolving or powering up. If at some point you want to power up the Snorlax but can't because of this, I would suggest walking a little with someone else (e.g. your Lapras) and then powering it up WHILE it's your buddy. It will probably maintain the difference if it is 'changed' while currently your buddy. Obviously test it with something you don't care about first though, as 600+km is no small feat (holy crap man).