Looking thru the web pages, NPM will only allow you save both historical and hourly data up to 180 days. In fact, you can set your data retention policies to keep the full historical data (every poll) for 180 days before this data is summarized into hourly statistics. If you were to use this setup, your database would actually then summarize from the detailed into daily because the maximum amount of hourly stats you can retain in the platform is for 180 days.
We run our platforms in various enviornments and many of our engineers and IT staff would like to be able to see this data for longer periods of time. For example, one of our groups is montoring our retail stores which are open from 8am to 8pm. As changes ocurr within our enviornement, they would like to be able to compare the current data against the data from a year ago. With the way NPM forces you to summarize the data into daily stats, this skews the data way too much to even be able to run this type of comparison.
I would like the ability to increase these hourly time period to a much larger interval (at least 1 full year). I would also like to see the ability added to keep historical data for that long as well. If one of our groups wants to spend the money on the extra storage requred to keep and maintain this data, i think the tool would be more useful to them as they could then compare "like" data.