My average speed is around 30 Kmh reaching around 45 Kmh on flat areas, but I doubt I could keep as high during more than 2-3 hours,

I went once with some girls who wanted to do the lake tour.

I had to wait for them as they rolled at under than 20 Kmh average.

There were not climbs on the Geneva-Lausanne-section, I guess maybe there would be some at montreaux, and by experience, the bike paths on the french side are less good than the swiss and in some places there is no bike path and you have to cross the french towns sometimes with a lot of traffic, usually many french cars that come back from Geneva.

When we reached Lausanne ( from Geneva ) after more than 3 hours then they gave up and decided to go back by train ....