It's easy to 'overdo' a skill if you're not careful. And it's not like a huge difference in the final product of that particular skill. But every time you spend SP's on a skill once it gets up into and past the 80 mark and every time you spend extra trains on it just to try to get it up real high, the less SP's and trains you have to address other important needs of your dot. It doesn't take much to 'overdo'... just a little too much can cause damage. I know... I've done it plenty of times.
