This post is two fold.

First: I use an intuos4 tablet and was wondering if any other intuos users have any advice on knowing when it is best to change the tips out.
Mine develop these annoying flat spots that tend to show up when I am trying to carefully draw a curve, which results in a bit of a jog in the line which then has to be redone.
How often do you change tips? is there away to round the flat spots out?
What tips are most efficient for workflow?

___

Second: I want to get back to basics with exercises. Is it more productive for building muscle memory to trace over circles, curves, etc., or should I only look at reference when practicing?

Thanks