Dan - thats my experience too - if every flower on the plant is going open centered, then its probably due to some sort of genetic loss, so it isn't going to get better. If I love it, I'll give it a 2nd year, but after that I'll toss them.
However - I have certainly had plants not do very well one year, produce hardly any blooms and just not look vigorous, and then have them be one of the best in the garden the following year.
When I think about it, I know that I have several plants that I have had since the beginning of my dahlia growing (10 yrs?) that just aren't what they were the first few years. I am not sure if I have just gotten pickier, or if they simply dont have all of their juice anymore. I have been growing just a single plant of most of them for years, and keeping one tuber out of 4-10 that are produced, is certainly not the way to improve your stock. I wish I had the room to grow 5-6 of each and then just keep tubers from the best plants. Or even better take cuttings like the brits do so that you have clones.
