The Problem with Shack Bags

So at some point in a relationship, you can begin to predict when you are most likely going to end up shacking with the person you're dating. (Shacking, as in spending the night). But there's this awkward time frame in any relationship where it's not SO DECIDED that you're welcome to stay with them any time you want, and so you're left with three options:

1. Just ask them if you should bring a shack-pack.
2. Pack one just in case.
3. Pack nothing, knowing you will be inconvenienced the next day by your lack of "supplies" and clean clothes.

I think this problem is worse for girls because it's just impossible to travel light as a woman. Particularly when you're staying at a guys house. If I were to get drunk and need to crash at a girlfriends house, there would already be the necessary hair dryer, smelly lotions, and probably even an article of clothing or two that I could borrow to get me through. But not so much with a guy...

So here are the problems with these options:
1. If you ask whether you'll be shacking, you sort of put the person on the spot, to where they can't say, "Uh, no. I don't want you to stay with me." Or if they do (even if it's for some very practical, legit reason), you can't help but feel stupid and take it personally. And even if they say yes, it's still just goofy to ask about.

2. There's no subtle way to bust out the prepacked bag if it does come out. I mean, how does that work. At whatever point in the night it becomes understood that you are staying, do you bust out with, "OK cool, hold on while I run out to my car to get the shack-bag that I packed just in case but wasn't positive I would need." How bad does that look? Or, the next morning do you just go out and get it and try to pretend like you just simply forgot something in your car?

3. And obviously packing nothing has its problems. No deodorant. No toothpaste. No clean underwear.