Many people change their identity much sooner than this. Significant relief from the intensity of homosexual feelings can also come much sooner. If God is part of the process, He will walk with you, protect you, direct your path, and shine His light into the darkness. Remember the ultimate goal in life is not heterosexuality versus homosexuality, but following God and giving one's life to Him. As with any deep personal issues which a person may want to change, there are no guaranteed results.
Many people do experience a complete change of sexual orientation.
Where before they were only attracted to the same sex, they are now only attracted to the opposite sex. Other people experience significant progress toward that goal. They may now be fully attracted to the opposite sex and ready for marriage, with very little same-sex attraction remaining. For others, there may be great change in their attraction toward the opposite sex without any change in their attraction to the same sex. Others still may become able to make healthy choices in terms of their behaviour yet find that their attractions and desires remain the same.