You'll want your concrete contractor to have at least 2-4 years of experience. However we recommend at least 6-7 years of experience. It is important to find a contractor who is proud of their work, and has references to support previous projects.
The amount of time depends on the size and complexity of the project. The timeframes tend to range from 2-3 days for smaller projects like driveways, or up to 1-2 weeks for larger projects.
Knowing the amount of people on the job and who is managing the project is key. You should always get a clear answer to this question. This also helps reinforce that your talking to an experienced concrete contractor.