How long does a turned off device stay operational? (main circuitry itself, screen, battery, storage -- whatever the devices they're using have) Also, we were a

How long does a turned off device stay operational? (main circuitry itself, screen, battery, storage -- whatever the devices they're using have) Also, we were able to decipher cuneiform because there were a lot of clay tablets available to study, but will people in, say, 2k to 4k years from now be able to decipher how to work the devices, its OS and access the library of data? Even my iPhone requires a surprisingly large amount of knowledge to access my various bits of data, if it were 4,000 years in the future and nobody understands English anymore, I can imagine it would be difficult to decipher. Perhaps we should be leaving a load of stone carvings somehow explaining how to operate the devices (and to read english, or whatever language) From the linked article: > "If we can nail the next 100 years, we figure we will be able to nail the next 100 years as well," Farquhar said. Except.. if there is a massive disaster event of sorts (WW3 was mentioned in the comments here), it may be longer than 100 years before somebody is in a position to access this archive. It may then be too late. Or the country is in crisis and the facility gets decommissioned or abandoned. I'm not saying they're not doing a great thing -- they are! I'm just concerned that it relies on a bit of luck.