For me at least, I don't think the G-1/G-2 lenses are worth the money compared to S-1 type lenses. They're good lenses, but a lot of their cost came from the fact that they were the only lens in town that passed that much light, and Laser66 was selling them for $25 each or something. Now with other sources of lenses, there are much more economical alternatives.
Plus, with the power levels lasers produce these days, even losing 100-200mW to losses doesn't matter all too much. I'd only be worried that back-reflections could damage the diode itself, but those S-1 lenses are pretty good anyway. If you're not building some 6W monster, you're probably okay. Even then, it may have been dirt or other problems that causes backwards reflections.
Also, if you want a good G-type lens, you can buy the bare G9 lenses from DTR (while supplies last!) and the empty barrels and
make your own. They're supposedly even better than the G-1/G-2 lenses. That's what I've done.
It's easy to do too. There are tutorials. After soaking in rubbing alcohol for a while, just get a pair of needle nose pliers and snap off the metal casing on the lens. Drop the lens in the barrel, screw it down, and you're done. It's the same process for bare G-1/G-2 lenses, only without the metal casing.
Buying G-series lenses for red may not be worth it anyway. The
acrylic red AR-coated lenses (deep blue coating) have some great transmission characteristics of all the lenses for red mostly because they're like those G-series lenses (single lens, coated). The red wavelengths also don't melt the plastic the way the shorter wavelengths do; though I haven't tried it for those 1W 638nm.
Lazeerer also had (has?) some AR coated single lenses for red as well. You can ask him about them.