I need to shorten a bunch of aluminum shafts and would like recommendations on removing the inserts and re-using them. I have limited resources (I'll be cutting the shafts with a tubing cutter and smoothing/chamfering with file) but plenty of time. Any advice?

Just put a field point in the arrow and heat the end of the shaft, pull on the end of the field point with a pair of pliers it should just slide right out. Instead of a file there may be a part of your tubing cutter that will chamfer the end of the arrow.

Thanks La.-I don't really have access to a torch, so I'll ask a  really dumb question. Other than a heat gun (if that would work), would a candle work?

And yes, my tubing cutter does have a wedge.

Yes

Or just hold the end in a pot of boiling water.

Heat gun, candle, boiling water, kitchen stove if your wife isnt looking all sound good to me.

Use vice grips for a good hold on the point.They can be stubborn sometimes.

For aluminum arrows, feel free to apply the heat directly to the shaft at the insert. If I don;t have access to a propane torch, a gas kitchen stove would be my next choice, since it won't leave soot behind.

If you going to use a torch,  use a low flame.  By getting the alum. shaft to hot, you will change the molecular structure of the alum and weaken it.  If your going to throw that part away,  then burn it up!