I am reading the analytics data using API call found in this link

It says that for all reports everything should be processed in 12 hours but it will depend greatly on the size of the properly. That being how many its your account is getting. If its a large account it could take more then 24 hours.

So how long you should weight will greatly depend upon how must data you have. Only you can decide. If its a big account with millions of hits a day i would go with the old 24 - 48 hour rule.

You could ofcouse just run a few tests. Check the data now store it and see what you get in two days if the data is the same then you will know your account processes faster then the 24 - 48 hour.