treated will last 15 years in wet soil, untreated about 2.
I didn't relish the thought of working with wet wood. So I
Broken panes are a fact of life with horti glass.
I wouldn't bother with anything frankly.
You will want to scrub it occasionally to remove dust dirt and lichen, anyway. Pressure washer good.
I had an old Al frame, and some of its glass. The glass didn't survive being stored, and nore did half th new glass carefully transported home. there was a bolt head under the boot carpet that cracked the lower sheets from the weight of the upper.
All in all the glass cost nearly as much as a new greenhouse would have.
Frames are cheap. Glass is not.