On average how often do asst coaches switch jobs

Great question and concern.  IMO, as far as choosing a school, yes the entire coaching staff is a major concern, right up there on par with academics, social life, geography, cost.    For pitchers, I would imagine the PC is hugely important?  Perhaps more so than some of the other specialty coaches for position players.  HC obviously most important of all. 

As far as the PC being there when you son gets there, my son too?  I'd say it's a lot like hoping for warm and sunny weather for opening day.  Yeah, it'd be nice, but clearly not something you can control.  At all.  And if in the end, the weather on opening day is 33-degrees and rainy?  It's still opening day and you play the game.

They do move around though.  I've told my 2018 to err on the side of making a contact with an AC if he can, even if the school the AC is at now, is not a school 2018 is interested in.  Because the chances are high that in the next two years that AC will be at a different school that you might be very interested in, or he could be a Head Coach at a school you are interested in.  So when he can, I tell my '18 to make the contact and establish that relationship now, even if the school AC is currently at is really not one he is very interested in. 

As my 2018 moves along in this process he will do less of that due to his recruitment time window closing.  As a rising HS senior or even junior not much point in wasting a coach's time if he is at a school you are definitely not interested in. 

Good post. Raises another danger to an early commitment--coach that "loved" you may not be there when you get to campus. Saw a good deal of movement amount A/Cs (in fact two RC's) during my son's recruitment process. We still haven't found out where one of them landed; one transferred  laterally within the same conference. This post gives players reasons to meet entire coaching staffs (cc: Rc or HC on e-mails) and to love the school for what it offers outside baseball.

Whether a head coach or an assistant, coaches are looking to position themselves to move up. An assistant will look to get behind a head coach who may be moving on or retiring. Or position himself on the right team or the right conference for exposure. 

As a player you can't control coach movement. A quality assistant is always a prospect for a head job. It means moving on. The only time a head coach typically isn't looking to move is when he's with a winning program at the top of the quality ladder (i.e. UNC, Texas, Vanderbilt, etc).