How long after tubes are tied do they naturally come untied?

1-10 years. Tubal ligation is very effective, but not foolproof. Conception after tubal ligation occurs in less than 1 percent of women. Tubes can come untied immediately or ten years later.
Never, usually. Surgeries to "tie the tubes" are meant to be permanent. Nevertheless, in about 1% of women, they become unblocked or were never truly blocked from the surgery. Your doctor can order an xray to check if needed. But usually that type of surgery is permanent, although some fertility specialists can perform a surgery to try to unblock the tubes.