As you probably know, some iris can be extremely robust, needing to be thinned out quite often. Immortality is a moderate grower that does not need frequent division. In my opinion, that's a really good trait! This pure white iris grows approximately 36" tall and I have yet to see it flop over. It is a multiple award winner and very popular. I don't grow a lot of iris, but Immortality is one of my favorites.
Rebloomers do like more water and fertilizer since they need an extra boost to flower again. You can fertilize them in early spring and again just after 4th of July. Iris like fertilizer with a low nitrogen content so as not to promote bacterial rot. Be sure not to put the fertilizer directly on the plant but sprinkle it on the ground around root zone area. You will be rewarded!