down here in Arizona, they can sit for years....in the right building. There are a lot of variables, it's hard to say how long it could sit in your available storage conditions, and with the prep work that was done on your specific car. More detailed info=more useful answers.
Lots of variables here. First, what is 'ready for paint'? Bare metal, treated with Ospho, ready for epoxy? in primer, really ready for paint? As squirel said, location means a lot. I'm guessing from your location, humidity is high and that will impact the answer. In general, if in primer and kept dry it would be OK for years. same if treated with something like Picklex20, my favorite. Sanded bare metal, high humidity, hours to days.
the body was down to bare metal then epoxy primer then high build. picklex 20 also my favorite thanks for your help
It sounds like you have a solid base there but I don't believe I would do a final sand until your ready for color
I've taken sometimes weeks to get something blocked for paint , final clean mask clean again and shoot , my last paint job was 20 years ago though .....