I hear where you're coming from, and DX teebird notwithstanding(cuz, let's face it, it's a DX teebird), I don't think your argument covers the full picture economically. For me, at least, my GL river has lasted through 2 DX leopards(and still going very strong), and while my fuse is relatively new to the bag, it's already lasted as long as my X comet and is still what I think of as "new". Keeping a prime x comet and dx leopard in my bag would cost me way more than my GL fuse and river.
Could be that I just don't like the leo and comet when they get super beat, but offered as an alternate opinion.