So today I say: Before throwing out your empties, make sure they're actually empty.
It might seem like a small difference, but every little bit helps. So if cutting open the tube gets you an extra 2 uses, and you have ie. 50 uses in total, then for every 25 tubes, you'll save one tube. Ideally, it'd be great to eliminate tubes, but if you're not there yet (and you're not alone) then might as well make the best of what you have!