Could the mirena (levonorgestrel) IUD be effective after 5yrs. Just used as IUD no hormones?

Not recommended. No, because it has no other chemicals like copper, hormones, etc, it will not really work to prevent fertilization. More worrisome, if fertilization and implantation occurs, the risk of an ectopic pregnancy is high. And, if a normal uterine pregnancy occurs, the iud will need to be removed and it is highly likely to cause an abortion.