FCP's legendary Lifetime Replacement Gaurantee. A lot of folks struggle with it. Here's how it works. Please read their info on this including exclusions, how-to, etc. on their website.
Buy part 1 for $X (please read their rules...it's all spelled out w/r to what is included...which is almost everything they sell including consumables). You have now spent $X. Use part 1. When part 1 needs to be replaced, you have to buy part 2. You have now spent $X times 2. Receive part 2. Replace part 1 with part 2. Fill out their online return form (which will have the original order# for part 1 and the new order# for part 2 that is replacing part 1,box up part 1, and return to FCP following their rules on your dollar. I suggest using pirateship and UPS for the lowest-cost return shipping. FCP recieves part 1 and credits your account with $X. You have now spent $X times 2 but recieved a credit for part 1 of $X so your next part 1 (or whatever you want to use the credit to buy) is free (or close enough - the prices fluctuate and generally go up over time but remember....you get $X as store credit, not whatever part 1 sells for today). Do this infinity until you sell your car. You will always be out $X times 2 b/c you don't return whatever you have in your car when you get rid of it/stop using part 1.
I've been doing this for 6 years and at this point have bought around $6K worth of maintenance/repair parts for all of our VW/Audis in the house and it's cost me less than half of that. It's a great deal if you keep track of it, follow the procedures, and bundle your returns.
How do they make money you might ask? B/c most folks 1) don't use it/think it's a hassle/don't buy enough to bother 2) if they do it's for just a few things so not a huge loss (more of a discount) and 3) oh look, while I'm here I'll buy (insert whatever you drop in your cart and don't ever return). Also, FCP is not cheap, they are full-price vs. many other places for parts so you are paying for it in the cost of every item basically.
Thanks for reading/attending my Ted talk.