You definitely don't need to tilt all the time. In fact, when it's more than 1/3 full, you can easily flood it that way (some worse than others). That's why I don't fill them all the way up - the thing wicks really well, and when it's more or less full, the physical shape has the wicks in the juice all the time, which can be good or bad, depending on how that particular Stardust feels about flooding.
Just dip the wicks once in a while. After a quick dip you should be good for three to 5 or so drags, depending on how thick your juice is and how long your drags. In my case I use 100% VG from Virgin Vapor (pretty thick, especially after sitting in the carto awhile), and I dip once and get four good drags out of it.
Once it's down to the bottom 1/3d, I more or less keep it horizontal just for the heck of it, and it doesn't flood.