Prior to performing the manicure, client will choose her/his polish. I give it a good shake. Yes, I shake the crap out of it, roll it upside down, right side up and check to see that those balls are moving freely! I will then perform my manicure and let the bubbles settle. I've never had a problem on myself or clients with bubbles or even tiny one's. I have checked this theory under a magnifier and I just don't feel that the polish get's mixed enough by rolling.
When you buy a can of paint for painting your walls, it will get put in an industrial agitator before you take it home. When it has been sitting for a while, you can still take it back to the store and they will mix it for free... for a reason. If it sits too long, it will settle and does need it. Nail polish is similar. Some have very fine pigments that settle on the bottom and won't mix completely with just rolling.
Without hijacking the post and trying to stay on topic, I have a couple of other questions:
1. I've had several clients that store their nail polish in the refrigerator. Does this prolong the life?
2. Does storing polish upside down also prolong the life?
3. Can any (professional) brand name thinner be used in most polishes? I have noticed that the odor is different so there is definitely different formulas and solvents.
4. Is there a thinner for Shellac and Gel Polish? (I've heard there is but haven't found it)