The OP is riding (probably as I write this) on a mountainous ride. I assumed that will include some mountain descents. Should the OP flat, for whatever reason, as he descends at say 45-50 mph, there is a good chance that an older tire will not stay on the rim. Should it come off, the odds of it jamming in the fork and stopping the front wheel abruptly are excellent.

Now, to answer coasting ... the ecological and societal damage caused by 1) the ambulance run to and from the site, 2) the medical waste (bandages, x-ray film, acres of packaging, etc. and the cost to society (loss of work time, etc.) will dwarf the ecological and societal costs of tossing that tire. Oh, and the fork on the bike will almost certainly be trash or highly suspect. Additional trash: bartape, brake lever hoods and possibly the levers themselves. Scrapes on at least one, probably two of bars, pedals and seat. Front wheel probably trashed.

I did this scenario except on the flat at about 23 mph and with a rear tire. Skipped the ambulance and took a taxi to a local urgent care unit. Since I was conscious, I had them only X-ray my shoulder (broken collarbone) and not my chest (cracked rib). So I minimized those costs but still, the acres of bandages I wore and changed daily added up easily to the ecological cost of a prematurely tossed tire. Had I been traveling at 1.5X or 2X that speed and had my front tire come off, my crash would have been far worse.

So, in my view, it is a matter of not just the likelihood of an event happening but also are the consequences of this unlikely event acceptable?

Ben