I live in Southern Pennsylvania and mine did not bloom well this year. Could it be the frigid winter or do they diminish as they age? Mine has been in the same spot for about 10 years and (I could be mistaken) but it seems to have less and less blooms each year.

Any thoughts?

Mine did quite well this year. There was even a surprise appearance from a hybrid I thought had died off a few years ago. And ten years isn't really that long for them. There are limits to their shade tolerance, though.

No idea why a healthy-looking stand would have scanty blooms (they're supposed to do well in a favorable spot and flower for decades). You could try taking stem cuttings and see if plants perform better in a different location.

I only have them growing in full sun, sandy loam soil. They've been growing in my butterfly beds since 2007. I winter sowed the seeds a friend gave me last year and have a dozen or so seedlings about 5" tall to plant out come fall.

As a side note on flopping... I gave up the peony rings years ago and just remove the seed pods.... Thick stems included... After flowering. The plant hasn't flopped since. You give up the neat look of the black seed pods, but it's worth it to me plus I don't get a ton of seedlings popping up everywhere in the spring like before.