It totally depends on several factors:
1. Mode of transportation (airplane v car)
2. Reason for trip (business v pleasure)
3. Climate you're going to (rainy v sunny v hot v cold)
4. What clothes you're packing
If I'm flying, I use a large tote as my "purse" and put a shoulder bag inside of the tote. If I'm driving, I tend to bring more purses since they're in my possession.
If it's business, I tend to bring my business tote, a shoulder bag, and a small evening bag. If it's pleasure, I tend to bring 1-2 anything bags, or a bag I don't usually wear at home.
As for climate, certain bags just don't do water/cold/heat, etc. But you know your collection best.
And as for clothing... I'm a minimalist at heart, so I always pack a lot of black so everything's good.
For instance, I went on a weekend trip recently with a
Coach weeekend bag and a backpack, carrying an older black Ergo purse. Now, I came back with 2 other purses, but I only had one for three days. Multifunction is the key.
Now, I'd never go on vacation with just a small pink clutch or something like that because I'd shop immediately!