Mirena. Mirena has more progesterone than Kyleena and can be left in place longer. Mirena lasts for seven years and contains 20mcg of levonorgestrel. Kyleena has 17.5 mcg and can be left in place for 5 years. Liletta has 19.5 mcg, but only lasts four years. Skyla has the lowest dose of progesterone at 14 mcg. It is only good for three years.