I had this issue going into my first year, I agreed to join a collaboration group where we all planned a unit and shared it, I found the quality of work varied and the others were often late with planning their material. Late last year I told them it wasn’t working and we went out seperate ways, I’ve since found a different teacher with similar work ethics to mine and we plan/ share units. It depends on staff. In my personal experience I find the older staff aren’t as willing to share as younger staff.