It is typical that coaches go and visit other coaches through out the off season.
Yep it is a very common practice - at least amongst offensive and defensive coordinators. A lot of times you will have coordinators going to visit other programs to look at how they implement their offenses / defenses, etc. Very, very common amongst the Air Raid / pass-oriented spread offense folks if I recall correctly.
Not sure if it is common with position coaches, though - I imagine it would be. Lots of benefits to it. I think a lot of "coach sharing" or whatever you want to call it takes place during the camp season.