[johnkeegan]

I just usually make a point of stopping by without notice to check on watering and remind them (in my stern "dad voice") that if they don't water as per instructions the guarantee is void. And I make a round of calls to recent planting customers if there is a prolonged dry spell. That works with 90% of the negligent ones. But some inevitably slip through the cracks and get free replacements despite their neglect. But to be honest, haven't most of us at one time or other returned something under warranty even though we knew we weren't totally innocent in the product malfunction. That's inevitable with any business that both offers a guarantee AND desires customer loyalty, whether it involves plants, trucks or cellphones (oops...did I say cellphones...).
On the flip side, the fact that every "landscaper" is expected to offer a one-year guarantee scares alot of wannabees out of the market. They either refuse to replace something that did die (new customer for me) or refuse to get involved with anything that grows. This means less competition and my guess is this helps explain why, in my case, there's more profit in planting than hardscaping. But we don't seem to have the influx of low ballers that plagues others. I think the cold weather and long winter weeds them out.