As Lorrie said, it depends on the nature of the work that you're looking at. If you're going to be supporting an outage as a tech or maintenance personell, then it would be a shorter term duration that could include time the outage for planning, during for the work, and maybe some after for cleanup / lessons learned.
If it is office work, project management, outage planning, engineering, again it depends on what the specific goal of your contract is but it could range from short term, < 30 days, to long term planning or projects lasting multiple years.
Don't worry about people saying it'll be for a day at a time, or that there are so many experienced people that will take the long term jobs that you'll be left with nothing. Throughout my career people have told me similar things trying to discourage me from going after what I want. Work hard, even if it's for 1 day at a time, and you're name will get around.