Last real system I worked on, I loaded the database with 100% fill of six months worth of data using redgate data generator. (3 million rows).

Six months was the retention period requirement.

Then I quadrupled the data i.e. 2 years worth. (12 million rows)

Half an hour or less was the process time limit for the big stored proc that generated the predictions - it ran just shy of eight. 😉

Job Done.

--Shaun