Your post didn't specify why you need to change the glass every couple of years ( cracking, discoloration, or hazing). A later post mentioned the spraying of glass cleaner and that brought to mind an experience I had with my first Franco Belge stove in 1983.
My stove door had a window consisting of 25 separate slats of glass, about 3/4" wide each. From time to time I would use a household glass cleaner to remove the fly ash which would collect. Not long afterwards, the glass became a bit discolored and very hazy to the point I could barely see the fire through it.
I visited a Franco Belge dealer(Coal Heat) in Emaus, PA(?) who was most helpful. He replaced all of the glass free of charge and cautioned me to never use glass cleaner again. It appears that when whatever residue of the glass cleaner is exposed to the intense heat of the coal fire, it becomes quite acidic and etches a haze into the glass.
From that point forward, I used either a spray-on oven cleaner or clean water to clean the glass. So far, so good. Good luck with your issue, and Happy New Year!