Assuming that you haven't grown it from seed, in which case you could be waiting 20 years with no guarantee that it will look like the parent's flowers. Most that are bought from nurseries are grafted and, with the correct pruning, should flower within 2 - 5 years. It's all in the pruning. Google 'pruning wisteria' for details.

I thaught without pruning aprox 7 years and with you could as you say get it flowering substantioly quicker but I stand corrected .