how much data does the mileage report hold before the unit ovwewrites the mileage .csv file

What unit/model?

Are you asking about the trip odometer or the track log?

I have a nuvi 205.

i have a csv file in the reports folder that only has 3 months worth of data in it. It should go back further in time because i bought 6 months ago.

here is what i want.

The csv file to get appended to each day with mileage, time, origin, destination so at the end of the year i can download it into excell and sum up the miles driven in a year or given time period for taxes and client billing.

can you please help??

The nuvi only keeps about 10,000 track points before it starts a new log. Here's a nice article describing the trip log (track log). http://home.comcast.net/~ghayman3/garmin.gps/page6.htm