Keep video for certain time frames based upon percentages? (85/13/2 breakdown) I'm trying to build an equation for an Excel spreadsheet that is used to calculate storage requirements for video retention over a given policy. Currently it works great for policies that only have one retention period where everything is kept for the full policy, but I need it to work against a retention policy where not everything is kept for the full policy.
What I am working with is this:
85% of videos are kept for 1 year (365 days)
13% of videos are kept for 3 years (1095 days)
2% of videos are kept for 5 years (1826 days, because leap year)
To test this i'm figuring 30 units recording per shift, 3 shifts per day, and each unit recording 2 hours of video per shift (180 hours of video per day).
From my figuring, 100% of videos are kept for 365 days. Only 15% of videos make it past the first year and then only 2% make it past 3 years. This amounts to:
Yr1   180*365 = 65,700
Yr2   27*365  = 9,855
Yr3   27*365  = 9,855
Yr4   3.6*365 = 1,314
Yr5   3.6*365 = 1,314
-----------------------
              = 88,038 Hours

Is my figuring correct?
Another way I looked at it was to average the days based on the percentage like this:
365*.85  = 310.25         = 55,845
1095*.13 = 142.35         = 25,623
1826*.02 = 36.52          = 6,573.6
-----------------------------------------
         = 489.12 Days    = 88,041.6 hrs

The problem with doing that is if I take 180*489.12 = 88,041.6 hours which doesn't match to my above figure of 88,038 hours. Which one is correct and where am I going wrong?

The second one is correct. In the first one you didn't take the extra leap day into account, but you did in the second. 
