I save the data from my Garmin onto GTC. I then export an xml file to Excel where I have a macro that reads the xml stuff and records the distance, time, altitude gained, heart rate zone times, cadence zone times, speed zone times, maximum vertical rate, and other data to a spreadsheet.

In the Excel file I have about 4 years worth of data from several Garmins and then about 10 years of data before that where I just recorded the time, distance, heart rate, etc. by hand off a regular speedometer.

With all that data, about the only thing I ever look at is the miles per month or year and the altitude gain per year.