Where you guys been, even the Energizer Maxx battery at Walmart has a 3 year replacement - 7 year (some battery types longer) prorated warranty. I haven't used the battery in a Grand Prix or Regal, but I used an Energizer Maxx battery in a 98 Expedition. The first one only lasted 2 years and was replaced for free. The replacement battery lasted about 6 years (which was longer than the crap battery ford put in from the factory. When the replacement battery went, it sat on the sidewalk hot for about a week. My friend and I were quite surprised it took that long for it to cool. I hate Walmart and try to steer clear of them for everything, but for $77 (Maxx-65N for an Expedition) , I'll use their battery. One problem which could be the vehicle or the battery was it had alot of white crap around both battery posts. I would clean it off, but it would come back in a few months.
If I were to get another type, I'd get an AcDelco factory replacement (think I remember is Gel) which is what is in the 98 Regal (besides the factory battery, this is only the second battery in the car) or an Optima battery (Gel) if I were running a large sound system like I did in my Grand Prix.