What a great subject. I tend to use white or cream CS and cut and fold at least half a pack ready to use. I sell my cards at work and find I use a white/cream base with lots of layers and bling. My layers are DSP or coloured CS cut to fit at the time.
I store my paper in huge stacks as I'm still waiting for the hubby to make some vertical shelving.
I have tried lots of different types of storage and vertical shelves seem to be the only safe solution for not damaging the CS. All my off-cuts (including tiny or oddly shaped pieces) are stored in clear plastic A4 envelopes with a press-stud fasteners. You can get these at local office suppliers. I used to dump all the off-cuts in a box and I ended up never touching them once they were in there. Now, if I need a small piece I pull out the specific named envelope and find a piece the right size before I cut into a pristine piece of CS.
So, yes, I precut some CS in readiness for a flurry of creativity. I rarely use a solid piece of coloured CS to make a card as they can be too dark and off-putting to write on for some people. The white or cream bases are also more affordable when making cards to sell. You can then afford to put more into the decoration and layers without overcapitalising on the card for sale.
I hope this helps,