I use the Hornady Unique for my bottleneck rifle loads, and don't clean it off afterward. Haven't had a problem yet, about 1K rounds.
I lube the outside of each of the first four or five cases, and then lube about every third to fifth case after that. I put a small bit of lube inside the neck of the first two, maybe three, cases, and then lube about every third to fifth case afterward.
I hate to say it's a feel thing, but it is a feel thing. I can feel when the sizing starts to get more difficult, and that's when I lube the next case. I can feel it on how the expander ball goes into the neck as well, and that's when it's time to lube inside the neck again. A little goes a long way.
chris