When I bought my '07 Silverado in April '07, the first thing I did was put it on a 3-stage desulphating charger. Now this charger has brought back batteries that should have been thrown away, so it's THE BEST charger I have ever owned.
I was listening to satellite radio while my brother & I installed all my accessories when I first bought it (tonneau cover, step rails, dual exhaust, cold-air intake, bed rails, etc etc....) -- took us about 8 solid hours, so that radio was on the entire time. I've done this in the past on vehicles with 250K+ miles & never had an issue, let alone a brand new vehicle. Battery was stone cold dead. So I threw it on that charger overnight & it brought it back like I expected, & probably saved it from an early death.
I have found this to be common practice in recent years on ANY new vehicle -- techs just don't spend the time to properly prepare a new battery, resulting in a VERY short life. This happened to a 2002 Suzuki DRZ400S that I bought new. I got 2 months out of that battery. My buddy bought the same model the same day & got 4 months!! My old man had issues with batteries in his '02 Silverado with a Duramax ....
The best thing to do if you either buy a battery from a chain store or buy a new vehicle, is make sure you have a 3 or 4 stage charger on hand (they'll run you 3 figures, but will pay for themselves in short order) & immediately throw that brand new battery on there for at LEAST 48 hours. Make sure that charger has a temperature sensor -- this is key. It will reduce current in hot weather ( or overheating battery) & increase current in cold weather. I haven't had a bum battery since, & actually have brought back to life 3 batteries, which other chargers could not save.
Bottom line -- don't trust any tech when it comes to batteries. Get the charger & do it yourself -- even if they tell you it's all set to go!