I always make sure that I have 50 copies available of the newest book with me, when it's first released. The other volumes, can have less. But, 10 is too low of a number and I need to print a new batch of 50.
I don't print every volume every year. If I'm hitting the same conventions, I have to make sure I have at least 15 copies of the older books. The majority will be buying the more recent volumes, not the oldest. But, if I'm hitting a new event or one I haven't done in a long time, I'll make sure to have at least 25 copies of each. It also depends on the size of the convention.
With that said, it also depends on the mode of transportation. If I have to fly, I'd go with my max of 50, but I'd cut down on everything else that I usually have on my table. If I'm flying to go somewhere, it means I'm hitting a very large convention, 3 days and more people. But, I don't want to get stuck paying high fees because my excess heavy baggage.
Train: You'll be dragging your stuff around. Lots of comics, means lots of weight.
Bus: If you're going by a travel bus, you'll be dragging your stuff around, but you're allowed more luggage and I have a foldable trolley that helps me roll my crap around. Public bus, is very awkward and I suggest a cab at that point.
Car:: As long as you don't mind doing tons of trips back to the car. You can bring as much as you want. I fill my car.
I've now done every single one of those modes of transportation. I'm just missing boat at this point. Maybe, when I hit Newfoundland.