Andy -

Just my $0.02 worth of experience:

I try to avoid fillets on simple shapes because yes, they are difficult to un-do. Instead I'll first try to build the fillet into the construction curves.

In the case of the capped, shelled cylinder, you can draw a 2D profile curve, apply the 2D fillet, and Rail Revolve into a cylinder having a thick wall. The advantage is you can simply move a couple of points and re-do the Revolve to get a new fillet dimension.

I also tend to save making fillets to the very end of the model creation so I don't paint myself into a corner.

Another thing I do on more complex projects is take a copy of the objects when they are in a less developed condition and paste them off to one side (or into another instance of MoI) as backup to an earlier revision.

Ed Ferguson