Well, most glass SP is not durable anyway.

If you see the glass panel of iPhone 4, 4S and 5, they actually got thin plastic bezel that runs around the panel. That may contribute to its relatively better resiliency (although of course, it's still breakable). Those are absent on the glass SPs in the market, so you'll likely break your SP much earlier before you hit 1-year mark.

Even the GLASt.R, which is dubbed to be much stronger than its non-rounded edge sibling, also doesn't provide significantly better protection.