As my makeup collection grew I realized that I couldn't use everything I bought at once so I left them in their packaging and kept them aside. When I see mascaras I want to try on discount I buy them and leave them unopened until my current mascara dries out. I have a huge obsession with signing up for freebies and samples. This habit got a bit out of control so I cut the top out of an empty tissue box (recycling!) and stuffed all the large-ish products into it and piled all my samples into a mini
In this way, I have a ton of shampoo, conditioner, hair treatment, lotion, and moisturizer samples to take with me when I go on a short trip and I have backups of a lot of essentials like eye primers and mascara. I use lip products really slowly so I set aside a few not to be opened till I'm finished with one that is opened already.
A few of the sample packets I've amassed over a pretty short period of time :) I sign up for a bunch of things online and samples usually take weeks or months to come so by then I'd forgotten that I had a sample coming. When I open my mailbox it's like a little present ^^
I also take out the sponge tip applicators in all of my palettes because I think they clutter up the packaging and it's a hassle when I'm in a hurry and I have to open the packaging slowly so the little applicator won't fly out. But I think they're pretty handy for un-pigmented shadows. I've been using these to apply the light pink The Face Shop eyeshadow featured in my Project 10 Pan.
A few things I have in my backup stash are a tinted moisturizer/foundation , Mac's Gold Mode pigment (pretty sure it'll take me years to finish the small bottle so not sure why I got the full size...),
ELF's shimmering facial whip (this was a free gift from ELF when I ordered from them), another L'Occitane hand cream, and a ton of mascaras, lipglosses, and eyelid primers.
I think it's a good idea to buy things when they're super duper cheap when you've been waiting to try them and to just keep them aside. So when you go on a makeup buying ban you can always go to your little stash and "shop" from there :) You never know what great products you might discover~