I hand-pollinated a butternut squash and I am curious whether they grow/mature as fast as a zucchini?
I would say it takes a couple of months for them to fully mature and develop their hard skin. Much more slowly than zucchinis (or courgettes as we call them in the UK). Once mature they keep well in a cool dark storage location.
I intend to leave most of mine until the plants wither and then I'll go round and collect all the squashes. This is in Cambridgeshire, UK and YMMV in another climate.