If you want to eat them for years to come, you need to replenish the soil annually, or dig them up and move them to new soil. If you leave any of the tubers are left, they can overtake big parts of your garden or beds. It's not easy to remove all of the roots, so prepare the area(s) you plan to use for them. They are not shade tolerate, so full sun is required.
Though they can be a bit of a pain to control, the plant offers a tasty bounty. You can dig them up and eat the root raw. You can cook them too. A little salt is all it really needs. They have a nutty taste. They are great for stews, a garish or as a side for a meal. The last thing I should mention is that if you fest on them, you might have a bit of wind afterwards, so just FYI. This can come in handle if you want to have a laugh post-dinner.