Thank you for your question and welcome to Just Answer.
As long as you can tolerate the tightness and the soreness that will come with wearing the retainer after such a long time, your teeth should shift back into the position that they were in when you first got it. It will probably take a few months for the teeth to get back to their original position so be patient. You will notice the the retainer starts to fit better and better as the teeth go back into position.
I hope you find this information helpful. If you have any concerns regarding this issue that I have not addressed, please let me know and I will get back to you with more information.
George McKee DDS
Yes you are correct. You will only have to wear them at night. I hope this helps.
You should wear the retainer all the time while moving your teeth back into position. If you try to just wear it at night while moving them back int position, they will move towards the correct position at night, while you are wearing them, then during the day, when you have them out, they will shift back to their old position. So you have to be tough and try to wear them as many hours during the day as possible. Once they are in their correct position, then you can go to wearing them just at night. I hope this helps.