Part of the appeal of a speed graphic is it's something cheap and functional for taking out in the snow. If I totally destroyed it, $200 could buy another, and that's the price of a single very cheap lens for 35mm. Chances are, nothing bad will happen to the speed from the weather as it's mostly pleather, vinyl, and aluminum.
I do not like others to accompany when shooting as many times I will just sit in the environment, listening and looking before I start. How long is too long? If you come up with an answer then you probably haven't spent long enough. I usually stop when my feet hurt, or freezing, or no more film. How long do you wait for subject matter to evolve in one place? Sometimes it never happens. If accompanying me please bring a book "War and Peace" would be appropriate, and please don't talk to me, or ask to look at the ground glass and then say "Hey, it's upside down"
The hardest part of actually shooting was keeping snow and ice from building up on the lens. Several exposures were ~10 minutes, so even though I'd clear it beforehand, halfway through the exposure it was building up. I found myself blowing on the lens to at least try to get the loose snow off. Haven't processed that film yet, so not sure if it had a negative effect or not.
The next day my shutter was acting a bit funky. I had to cock it, press the shutter release, then fiddle with the cocking lever to get the shutter to fire. A few hours later, it was fine (probably just still a little wet inside). I also had water inbetween my GG and Fresnel, but I just took them apart and let them dry.
I think the only real concern with getting these cameras wet would be (a) rust and (b) getting the inside of the bellows wet, where (at least on mine) it doesn't appear to be water-resistant. But, I think as long as you immediately dry it when you get home it should be fine. In the future, I plan on using a blow drier and a can of compressed air to dry it out before letting it sit overnight.
When I get my Crown Graphic, I think that and my Ilex 150mm will become my designated "poor weather" setup.
Here's my snow results, at least some of them. Still got another sheet needing to process. mfratt; cool pix of your cam all covered in snow! I was only doing handheld exposure, so I didn't have to leave my speed graphic in one place quite so long.
I love the effect snow has when it builds up on the side of things like that. I think your second photo is the strongest, but they're all really nice. Can't wait to get around to processing what I've shot (need to buy some more chemistry).