It all depends if you are taking downstream or upstream cruise.
Downstream is usually from Chongqing to Yichnag and takes three days. This cruise is very popular with Chinese people as they think if you go downstream everything in your life would go easy, with stream flow.
Upstream takes longer and last 4 days from Yichang to Chongqing.
There is Victoria Cruises which sail from Shanghai to Chongqing and it takes 9 days. THE Cruise From Chongqing to Shanghai takes 8 days.

I joined a cruise last year, from Yichang to Chongqing. The cruise lasted for 5 days 4 nights, it was great. However, after I finished the tour, I found the down stream cruise from Chongqing to Yichang which lasts for 3 nights could be better. Then I could save time for other cities. I heard there is also a longer line from Chongqing to Shanghai.