Hi Gregg,
Thank you for your question. The product should stay good while you install a couple of stairs per night. Just make sure you seal the can and/or cartridge. As for the amount, it will depend on the linear feet of each step. Without knowing the exact width, it's hard for us to tell. Here is our recommendation, 1/2 in. bead of approx 40 lin. ft. per two part quart unit, 1/4 in. bead of approx. 50 lin. ft. per dual cartridge. Also, feel free to call our product specialists on Monday.
Thank you,
The Koffler Team