How much time the case lasts after the expedition?

Is it work related H1b premium processing? It's 15 days for processing, not guarantee for an approval though.

do you sugest the expediting the case ends up in negative decisions? I applied for the O1 visa from B1.

O-1 visa needs a lot of supporting documents and therefore
premium processing often request RFE on this matter.If you think your documentations on changing from B-1 to O-1,then proceed with the filing thru premium processing.
It would be best for us if you can tell us briefly on your qualification to have O-1 visa and we'll hear better suggestion from the board.Wishing you the best of luck.

What is RFE that this O1 needs. I am a ballroom dancer and was offered a job here as a teacher instructor. I came here on B1 visa and now my employer hired an attorney to change my status into O1.

You are confusing O-1 visa with P- 1 visa.O-1 visa is given to individual with exceptional talents in the field of sciences,arts, business or athletes.INS easily approves if you are a Nobel prize awardee or Olympic medalists.
You might be needing P-1 visa as this is for those who are internationally recognized entertainers or athletes.But just the same any immigration lawyers know that they have a hard time documenting this O-visa as it is second hardest to asylum.Wishing you luck anyway.