If you can only have a couple hours data loss at the max, then enable Full recovery model and setup a backup schedule for your tran logs.
As for the duration of the backup:
A differential will backup the changes since the last full all the way to the current. Thus, over time the differential will start taking longer and start getting bigger. But that seems like the closest to what you want.
Jason...AKA CirqueDeSQLeil
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I have given a name to my pain...MCM SQL Server, MVP
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