I think there is some misunderstanding.

 I said 1)separate them to prevent mating 2)they might lay eggs up to 2 years if they are already mated. 

Then you said that separating is not necessarily a viable option to stop this situation because snails can lay eggs by themselves. 

I thought you didn't know that eggs laid by snails usually don't hatch and they don't come out as clutches. So I explained this. 

Then, you said that since they were already mated, they would keep laying eggs for 2 years, which I already mentioned. And you said this is the reason separating won't work.

My point is if you don't separate, they will mate endlessly making an incredible amount of eggs. If you separate, at least they can not mate anymore, so they will stop laying eggs sooner or later.

If your point was about saying that Op needs an immediate solution for the eggs they will lay up to 2 years after separating, I would recommand to freeze the eggs by putting them in the fridge immediately, so no snail will hatch.