Is it important to get dual pane windows?

We like the benefits and always order insulated glass. On our last trailer we had one go back after 3 years and Forest River took care of it. Now we have one that is about 18 months old with a bad sash.

I've been trying for over a month to buy a replacement from Hehr Window company, let's just say they don't have the best customer service. Ask about warranty and who made the windows.