Offshore Wind Turbines Could Power Atlantic Seaboard

I am curious what the real life time costs are for wind power. I've seen numbers thrown around, but not sure what to believe.

Land based fossil fuel (oil and coal) power plants are generally designed for long term use (50+ years), there are design and manufacturing costs, maintenance expenses to keep them operating and of course the expense of the fuel as well as the operating expense of converting the fuel to electricity.

What time frame are wind turbines being designed for? For sea based wind farms, I would expect the design and manufacturing costs to be substantially higher than land based wind farms just do to the location and the fact that they operate in a rather caustic environment. How do maintenance costs compare? Labor expenses may be high based on specialized labor to sea based repairs. Are the designs reliable enough to last 50 years? Is the 'free fuel' enough to offset the other expenses to make wind based energy competitive with land based fossil fuels?

On a visit to the Challicum heights wind farm in Australia, an engineer mentioned the power cost " is about 3 times the price of coal". That's on fixed solid ground, near infrastructure and close to the power grid.

Mid ocean systems might be slightly more.

Depends on how well you build them. Holland has windmills 100's of years old.

Yes, I agree....but the phrase 'how well you build them' is not quantitative.

Are Holland's 100 year old windmills out in the middle of the ocean where they have to withstand constant loading of sea currents as well as the wind currents in a salt water environment?

Are Holland's 100 year old windmills designed to produce electricity? If so, what amount? I believe those factors play a part in the expense of the mechanism.

The questions I raised in my original post were intended to put things into the context of being economically feasible.