We’re optimizing for cost here, nothing else matters. You can always turn off a wind turbine.

If you’re proposing seasonal storage as a viable option then cutting total storage needs by 90% (to handle a 10 day lull vs 90 day gap) is inherently cheaper.

Hell traditional hydro is well suited for such situations as annual output and storage is limited but nontrivial. Doubling output for 10 days isn’t nearly as problematic as trying to cover a 90 day shortfall.