I have a dremel I have had since before the crusades, so the cutoff wheels last as long as it takes to install them. One of these days I am gonna invest in a new model and accessories.
I haven't addressed this properly because so far the 3 inch air die grinder or the 4 inch Makita electric have worked okay. When getting in to close areas, an air body saw finishes. Still I hear good things about the newer Dremel.