Is there’s limit on 144 hour visas

Geoff, you have supplied just a portion of necessary information for us to be able to offer a reliable answer.

As we can see, your flights to and from Shanghai will not have any additional landing within mainland China. This is fine.

Now, it should be important to see whether your cruise will have any ports of call within mainland China beside Shanghai, of course. If this is not a case, even this portion is fine.

To conclude, if the above mentioned details are as we have concluded, you will be definitely eligible for 144 hour visa free transit in Shanghai twice and you don't need any kind of visa.

In reality, there is no limit on how many times you can use this scheme and also there is no limit on how often you can use it. So, there is no problem even in this regard.