There is a thread on this page called "Good article on heucheras" -- the article it refers to is full of good info, and it suggests that heuchs require dividing every 3 or 4 years. I admit that I have several that are much older than that and have never been divided, but I have little space for duplicates so there is no encouragement for me to do it.
Jan

Thanks Jan,
It was a good article.
I have little space too, but my one sun bed is now becoming more and more shade. I need to dig up a aster and move it to my front bed so I might try digging up a brownie and putting it there.