"
Weatherlink software for Vantage Pro comes with a data logger which,
at a guess, would hold around 10 days data on a 10 minute archive
interval. Archive interval can be set from 1 minute to 2 hours with a
proportional data storage period -- I normally use 30 minutes which
provides comprehensive data that isn't too tedious to search. It's
easily changed if you require more data for a particular purpose, or
longer storage without downloading.

On a 15min archive the logger will hold approximately 28 days of data, I
can't find the exact figure at the moment.

Alan