Some people buy head gasket sealer from auto parts stores and dip the tops of the tubes in that. It hardens and is very heat resistant. Might be cheaper but I'm not sure how well it would work in comparison to the bands.
I've seen really heavy brass ring retainers with padding sold in hi-fi boutique places. The idea is that the added weight dampens vibrations better. The glass in a tube expands with heat so you need something that gives between the glass and metal rings. I've never tried these myself. Too pricey.
It seems to make sense to me that anything that would keep the tube from being shaken by vibrations might increase its lifespan and performance, especially if your tubes are expensive....but I've only tried the rubber ring kind of dampers.