In some climates, you don't have to dig every year. I used to not dig every year and dug in the spring instead, chose a tuber that looked good to put back in the hole and gave the rest away, or planted the extras someplace else. More often than not, when I dug in the spring, there was something I could put in the ground. But about 3 springs ago, I went out to my garden of about 150 plants and all except for maybe 8 of my plants were 100% rotted. There had been an early hard frost followed by rain, rain and more rain. It was spendy to try to replace just my favorite varieties. Further, I was trying to replace favorite varieties long after most of the tuber inventories had been well picked over. That's why I dig every fall now. Come spring, I know what I have, and what I really will feel the need to replace because I've been through my storage boxes and I know what I have and don't have.

Why dig at all? Because the tubers multiply and deplete the soil. Because your flowers will get smaller. Because if you ever do decide to dig, and it's been more than 2 years, digging will be a mess.