average time before corrupt data.img?

[gTen]

In terms of data corruption when the file system is not journaled, the best practice is to avoid shut downs when battery is low and to avoid pulling the battery and instead using the built in reboot/shutdown.

Also to keep in mind SD cards are not exactly meant for high consecutive writes. Doing so eats away their lifespan. Though the controller usually distributes the writing so it does not happen onto the same block too many times, this is why its good to have as much free space as possible.