I have a 2006 z71 5.3L 1500 Chevrolet Suburban and last month decided to get a MTP-78 Interstate Battery. I was told by the dealer it was new and when he installed it he went to the warehouse across the street and brought it back to the shop and installed it for me. The battery has a 30 month free replacement warranty on it (thankfully) however, my question is should a "new" Interstate battery go bad that quick? Or was I perhaps sold an Interstate Battery that just looks new? Any thoughts and/or suggestions as to what I should do? Thank you!
Any new part can be defective, that's why you have a warranty.
Some places are harder on batteries than others.
When I used to live in south Georgia, the extreme heat killed batteries very quickly. I did good to have them last 3 years.
Now I live in upstate new york, and have seen 10+ year old batteries doing fine.
A 30 month replacement warranty is not bad.
Well I guess living in Florida is not helping. Lol Thank you! 
Yeah, the only good thing is, you may get two batteries out of it, and maybe get five years or so anyway.
Your car had a 60,000 mile warranty, but you would probably be upset if it only made it to 60,001 miles. 30 months is better than nothing.
You can find out when the battery was manufactured (other manufacturers make it easier) to see if it was a"fresh" battery
https://itstillruns.com/manufacture-date-interstate-batteries-8192048.html
Thank you for this link.