Really. The caps and gaskets aren't all that great, I found with mine after opening and closing them a bunch of times they will start to seep a little. Replacing one or both solves it, and if you just put them on and leave them alone they won't leak.
Also, on the cap that raised section of plastic on the cap is a vent, and it works best if that's at the highest point- ie, don't put that facing the front of the car, because when you stand on the brakes the fluid shift will put fluid out the vent.