It is the opposite. Fermenting lowers the pH of the cream, making it taste sour. And the time you can ferment it is limited by how sour you can stand to eat it. If you ferment it for too long, the taste will be simply unpleasant.
Typical fermentation times are similar to yogurt and will depend on your culture. I ferment with thermophillic lactobacilii ...
I make yoghurt without pre-heating the milk and it has come out super 6 or 7 times now. I use the cheapest milk from the supermarket.
I do sometimes strain it a bit and it becomes even thicker and creamier.