If you freeze the chocolate, it'll likely "bloom" (some of the cocoa butter will separate out, leaving white spots). This is an entirely aesthetic problem; they'll be perfectly safe to eat, and it doesn't affect the flavor much. So, you may want to try this for your personal treats.
The filling may or may not freeze well, depends on what the filling is. First, if its a fairly concentrated sugar syrup, then it may not freeze (because the freezer isn't cold enough, it'll just get really thick). But it'll last much longer. Most fillings are also perfectly happy in the fridge, and will last longer that way too (but not as long as in the freezer).
Other fillings may suffer texture changes. E.g., freezing may separate any emulsion.
You probably won't have issues with water escaping, as your fillings should all be low-water anyway.
As with anything in the freezer, tight moisture and air impermeable packaging will work best.
Like so many things, if you know what you are trying to do, fudge is not difficult to get right.
Fudge is a high fat candy. In the US chocolate is implied but the addition of chocolate doesn't change the process.
You want a solid, creamy candy with a smooth texture.
As Elendil wrote, it is important to ensure that you cook the candy to the correct temperature- but that is only half of the problem.
As the candy cools it will form crystals. In order to have a smooth texture you have to make those crystals as small as possible. The bigger they are the grainier the candy will be. The slower the crystals form the larger they will be able to grow.
For a smooth texture we want to form crystals as quickly as possible.
Crystals require a trigger to set them off- such as a seed crystal or agitation. If the candy is allowed to cool undisturbed and with no seed sugar crystals in the pot no crystals will form. It will be like a bomb ready to go off at the slightest provocation- this is what we want. After it is cooled we stir it like mad to form all our crystals all at once- fast and small.
Fudge is very forgiving in that it is easy to start over. Unlike an egg custard that when it breaks is unrecoverable- the sugar crystals that ruin fudge are easy to fix. You just add a little water, melt the candy back down, and start over.
Tricks to prevent premature crystallization
- Prevent errant crystals!
A lid is placed on the pot for the last few minutes of cooking. This causes condensation to wash any errant sugar crystals off of the sides of the pot. A single errant crystal can ruin your fudge.
- Don't agitate the candy
When the candy is cooling it can't be stirred or bumped.
- Add distractions
I consider this cheating and it is unnecessary but some recipes reduce the risk of premature crystallization by adding things like corn syrup or marshmallow creme.
Best Answer
Fudge really only has a shelf life of a week or two. First it will start to crystallize on the outside (which is actually very yummy in my opinion), but then it will start to grow mold. Good hygiene will lengthen the time before mold starts to grow, but ultimately fudge is not a preserved food and isn't meant to keep. The individual ingredients will keep better by themselves, and you can make the fudge nearly on demand.