Best time to make Altbayern part of Austria?

What would be the best time to make Altbayern part of Austria? Although I put this in the forum "before 1900", feel free to pick a later point of time if you think that is appropriate.
 
War of Spanish Succession. They had already over run and pacified the area. This would very well set them on the path of uniting Germany. Silesia would likely be retained, the rise of Prussia stunted and the resurgence of Imperial influence quite possible.
 
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