Most conditioners/waxes won't last forever. There are several out on the market that will work. I use Leather Balm. It's easy to use and shines up well. Recently I've used pure lanolin for testing some techniques. It sure repels well. For ease of use Leather Balm is my choice.
Nice job! Isn't it amazing how much leather you use for something like this? I'm in the process of making a saddle bag and WOW it takes a lot of leather.