Unfortunately much of what you describe also applies to what I see here over a five year period. Good start, good first and maybe good second season and then decline. A few do well, but a lot more decline. Medians as a group do miserably here, so there is no alternative to TBs. It's not only just cold climates. My climate wouldn't qualify there at all. Choosing award winners isn't a good method for predicting performance - hardly any have done well here. Different plants probably have inherent preferences concerning amount of rainfall, ability to withstand scorching heat as well as brutal cold. The best choice is always to observe what does well in the area. But that limits choices to older types and a very narrow selection. Long ago I resigned myself to the fact that much of what appeals to me may not be durable, and accepted that the only way to know is to try them and see. Historics are a better bet, but not by the margin you'd expect. Which may explain why the range of what is grown in the area is so slim.
Texas Zone 7b, USA