I made the realization a while ago that no matter how badly I wanted to use everything I had in my stash, that it would never, ever happen.
I spent an entire day sorting things by type (cleanser, toner, cream etc) and laid them out in front of me all over the living room floor. I have dates on most of them so I ordered them by date as best as I could.
It's so hard to get rid of stuff I really want to use, so basically I played a little game. I wanted to get rid of at least 30% of each "group" unless I didn't have many items in a particular category. So in order to help me decide which products to get rid of, I shopped each section one item at a time.
Basically, I looked at the cleansers and chose the one I would want to use next. Then I went to the toners and did the same thing. Finally I'd have 3-4 products left in each pile, and I knew that even if I was interested in using them, they were the last ones I would pick, so it's time to get rid of them.
Then, I made a pinterest board with a photo of each product. I put it's meme listed price, and then took about 70% off of that. I posted the pinterest board on the memebox addicts facebook group and asked buyers to pay for shipping since the prices were very low, and bam- I made some extra money AND got rid of excess product.
That way, I can use the money i made to buy things I've really wanted to try, or things that have been on my wishlist for awhile, rather than holding on to a huge excess of product that I'll never get around to using!