I think its a percentage thing, like if it goes bad within the first 3 months they might give you 25% off or something like that, not sure on the exact numbers.

batteries aren't covered by verizon warranty that's why they don't send you a new battery when you do a FRU. you might talk to the store that you bought your phone from, they might be able to offer you a couple of options, but unfortunately verizon doesn't warranty batteries

batteries are covered under atiered warranty. 1-3 months you get a free replacement if defective. 4-6 months you get %50 off retail, 7-12 mo you get %25 off retail.

PMFJI
I'd do a search on ebay, and look for a 'new' or like new battery. New for the V3m seems to run ~$12 and like new (not new but good) about $5-6 delivered.
I bought a small desktop charger for $5, too and just cycle through batteries. Cheaper than trying to do a pro rata replacement, and you have a back up.

Not sure why this is but I am at a premium agent location we will swap you out up to one year Free on bad batteries, I can also honor that if you didn't get it from me I just need the receipt from when you bought the phone.I give you new batter, take your old one and manufacturer swaps me for a new one and I put it back on he wall. Your battery is covered by the manufacturer for one year, if verizson is not going to honor it then call the manufacturer. Plus depending on the phone(example moto 325) sometimes they are aware of battery issues on certain models. The corp stores by me have been swapping out for free battery on the 325 because of a known issue.