The time it takes for a tax preparer to complete your taxes will depend on a number of factors, including the complexity of your return and the efficiency of the tax preparation service. A professional tax preparer may be able to complete and file your taxes in as little as a few hours, or it may take several days or weeks depending on your needs and situation.
Truly, the best way to find out how long it will take for a tax preparer to do your taxes is to consult with a tax professional directly.