I purged my stash several years ago when it became apparent that I wasn't 'in the hobby' anymore. Allocating time towards modeling wasn't possible. I had no time for myself, and what time I did have was put to other uses.
Looking back I wish I would have hung on to them, since I made it back into the fold of building again. Oh well, live and learn. What I have learned is that staring at the stash can be depressing, in fact you'll never build but a small fraction of them especially 3000 kits.
As an investment, we all know that in most cases they will never garner the return we expect. We all know the term 'Rereleased or Re-issued'. If the initial run was short, the box art rare, they might have added value to someone.
Holding onto supplies such as paints and putties can be totally a waste of time especially if they dry up or go bad.
By not taking the time to sit down and start building now, you'll enevitably reach a point in your life where you'll have the time, but have lost the physical ability to do so. The eyes go, hands shake or your body has nasty reactions to the solvents and paint fumes.
Occasionally you read where someone is sacraficing their collect because of an economic down turn in their life. Unemployment and a mortgage or other debts usually don't team well. For some, this is an end to their involvement in the hobby. For others it is a means to purge and renew once the uneasement passes.
My suggestion for what it is worth, start building and purge the items you know you'll never build. Donate some to your local Boys & Girls Club that has a model building program or offer to support one with your kits and your time. If you're involved in a club, donate them as door/raffle prizes. It may be painful at first but it will help you stave off the depression of watch the stack slowly dissappear. Or you can sell them on eBay. Someone wants to be in the same situation you are in, let them suffer too. Or since you have 3000 kits, why not open your own store!