I have bulbs 15-20 years old. You can keep repeating this process indefinitely. I take mine out of their pots and plant them directly in my compost-laden zone 5 garden in late spring, then bring them in before frost. I just brought all 64 in this weekend; about 1/2 are blooming size, the others need to grow for a year or two yet. I've only bought 5 bulbs over the years; the rest are all babies from the bigger bulbs. Some of my bulbs are huge; it's not unusual for them to produce two or three flower stalks with 6 flowers each.