I don't deadhead mine; I've been completely enjoying growing these from seed. And, I've been pleased with the flowering performance after letting them set seed - the plants don't appear exhausted to me, but

According to an article on hellebores by Hinkley, Heronswood, that I saved -

"Unless you wish to collect seed to sow for additional plants, consider removing the spent flowering stems to retain vigor of the parent and prevent self sown seedlings."

(Now, why you'd want to prevent self sown seedlings when they tranplant to be shared so easily, I don't know...but this is the word from the Heronswood guru :) )

Thanks. I'll try to leave them on for one season and see how it goes.