We had an area of delamination under a window, ours is a 2010 ElkRidge... I found it in August of 2011, 5 mo out of warranty... in one month it appeared suddenly. I had proof that I had done the required caulk maintenance, and we had experienced record drought. After the window was professionally removed and detailed pics sent to HL, they agreed to help take care of the cost. No fault was admitted directly. If I were you, I would take pics, and contact Heartland that you want to see if this is indeed a water infiltration or a defective wall panel. Don't cast blame. They can recommend some independent repair facilities that can look at it in a timely manner. Then, go from there. If you know you haven't checked the caulk and it's been 3 years, chances are they will not help. But if you have been diligent and check and recaulk as recommended and/or the repair facility cannot find evidence of water infiltration, then Heartland will most likely step up and help.
Caulk should be checked every 3 months, according to what I heard. Now should it be redone every time? I'm not sure. But if you're watching it and checking carefully every 3 mo., you'll catch a place where it has cracked or started to look chalky way before major damage can occur.
On our coach, in three years, some areas have been recaulked 2-3 times.
Erika