With a small crew 4-6 people I always plan at least two days with no chance of rain. On larger jobs I like at least three good days straight.
On new roofs I've papered and shingled while raining more times that I'd ever like to admit. I saw my father fall off a 7/12 10 years ago while papering while raining.
I've papered over ice many times but always have waited until the ice melted prior to shingling. It's funny how builders don't care about roofs being put on poorly in the Winter when inspections are close.
A couple jobs done during the Winter have resulted in popped nails all over the roof. In the past 10 years 3/4 of my roofs were stapled and I never had any popped staples. Right now I've got a roof with tons of popped nails done last Winter. Makes me want to go back to stapling, never had call backs when I stapled. Thinking the popped nails were due to either lousy OSB or roofing over wet OSB.