You see, it is a one thing to play them for your own enjoyment only. It is completely different thing to master these pieces and prepare for public recital.
While practicing for your own enjoyment you can be quite satisfied with your results even though you make quite a few mistakes. This way your organ playing still sounds nice to you but it's a different matter when you want to prepare for an organ recital.
You see, some organ recitals are not free and people have to buy tickets. So you have to be in a superb shape during an organ recital otherwise people will not be happy with your results and will feel that they were cheated.
So if you want to be in your best shape and play without mistakes during your recital, you have to have a plan. This plan should include specific steps of what you need to do and learn each and every week in order to get to your goal on time.
Remember to set your goal date one month earlier than the recital because you have to be ready and prepared at least 30 days in advance. This will give you the time to thoroughly master these pieces.
This way when you have your plan, I will recommend to master your pieces by memorizing them. You see, although memorization is not required in an organ recital and you most likely will not play your pieces from memory during your public performance but practicing and memorizing these pieces for your own benefit will be of great help in preparation for you.
Therefore your plan and steps should include procedures on how to memorize your each and every piece.
The next thing to remember is that the recitals usually include at least half an hour of organ music and most likely more. Generally speaking, the average length of an organ recital is about 1 hour. This means about 50 minutes of pure organ music without stops and registration changes.
So in order to be prepared for your public recital you should be practicing in a way that in your practice sessions you will be perfecting your entire recital repertoire.
Unless you have 3 or 4 hours a day to prepare for the recital, it is not technically possible to practice all 50 minutes of organ music during one practice session every day.
What I would like to recommend is to subdivide your program into two halves and practice the 1st half on day 1 and the 2nd half on day 2 and so on. In other words, alternate the two halves of your program every two days.
This way you will be able to play the pieces and perfect previously mastered material on a deeper level than just practicing playing one time through for all 50 minutes of organ music.
Apply these tips in your practice as you prepare for organ recitals and remember to schedule and set a date at least one month before, stick to your plan and you will succeed in preparing for public performance.