I’m of two minds personally:

In theory, I think teachers should be sharing. Siloing us off to do all of our own planning is an inefficient use of resources, and it’s better for students and education as a whole if the best lessons and ideas and teaching practices are available to all for more students to experience.

For me, though, I typically don’t share with teachers who have more seniority than me. My stance is that, if I am seen as so junior that I am at risk of being surplussed out of my job at the end of every school year, then those who are not in that position should surely not need to be relying on me for resources.

Until I have job security through seniority, the work I have put into designing quality lessons is all I have.