Not to start a debate, but TWICE I have had to buy a battery to get me out of a jamb. Even if the battery hasn't gone south being able to find a open store is helpful.
One time was, I stopped at a rest area for a break in a pickup. Went to leave and no juice. Oh great now what. Battery was discharged, who knows why (old battery). Have to get home this evening as I have to work the next day. Just so happens a Wal-mart is just up the road. A great fellow gave me a ride and I bought a battery and made it home.
I am sure that the plates or something shorted together, because when we tried to hook up the jumper cables the sparks flew. So yea it only took about 5 minutes to decide I needed a battery. Also had to put a alternator on it a couple weeks later.
Now if I had broke at home or work and could have checked with a Hydrometer and a Load tester, Then try a recharge that would be a perfect situation, wouldn't it?, But a rest area isn't the best place to work on or diagnose vehicle problems.
I work on heavy equipment for a living and I have seen new batteries give up for no reason, and I have seen old ones last longer than they should. There is no super way to tell when they will die. The trick with being on the road is to have a "what if" plan.