So I've been reloading for 30 plus years and all this time I've only done full length resizing. I've always heard that neck only sizing is easier on the brass and with the rising cost of brass I think I might start neck sizing only. Are there other benefits, problems and or misconceptions that I should keep in mind?

I generally collet size most everything. In my experience, if you can keep loads moderate you can get fantastic case life. A few things come to mind.

Its rifle specific, neck sized ammo may not work well in another rifle so if you run multiple rifles in the same chambering you will want to segregate brass.

Every know and then you will have to full size or use a body die to size the shoulder back. I like the redding body die myself.

So if its rifle specific, does that mean I need a neck die for every rifle of the same caliber? I dont understand how its rifle specific. Are the neck dies adjustable or what? Why wont the same die work for multiple guns? Is a body die different from a full length sizer die and if so how?

Neck Dies are adjustable, but you won't likely need to between rifles. Its the brass you won't want to move from rifle to rifle, because each rifle will have slightly different headspace and the brass will expand to fit that headspace.

A body die is like a full length die but doesn't size the neck just the shoulder/body. I typically use a body die to push the shoulder back when chambering gets tight, When I do that I also trim, chamfer and anneal, then neck (collet) size. It varies a little but as a guess every 5 or 6 loadings. All the other loadings I just collet size and reload.

So a body die is essentially a full length die with the expander removed?

No it doesn't size the neck down or expand it back up. After using the body die you would need to neck size. you are correct it doesn't have a spindle so it won't deprime either.

So does a neck sizer have a depriming rod or not.

Yes it de-primes on a standard neck sizer.

Not the same but you could experiment with the full length sizer by stopping just short of the neck shoulder junction. We used to call this partial sizing and it is not the same as using a true neck size die. But it will tell you if your cases will work in multiple rifles before you buy new dies.

That will only work if the body section of the die doesn't squeeze the shoulder forward.

Lee collet neck sizer to decap and neck size. Redding body die when the shoulder needs to be bumped back. Anneal every 4th load.

Lee also makes a deprimer, which does nothing but deprime, it works for multiple cartridges. You can deprime and then clean the brass before worrying about how you want to go about sizing it.

Universal de-primer is a good way to keep your dies free of the primer residue and carbon. I use it on a separate press.