Ripening time depends on location and temperature. In my yard everything takes at least 6 months, including Dwarf Cavendish.
I'd say if they are not plump before the first frost is predicted you should cover them with a makeshift greenhouse, and add a heat matt or x-mas lights to help keep the soil warm. They will ripen at pretty much any stage of development but flavor and texture will be better with some maturity.
Great picture btw!!
