What OP is discussing (among other things) is called "bit rot" (among other terms). Just powering them up periodically for magnetic media isn't the complete solution. You need to read and re-write the data. In the old days, there was a product called Spinrite that basically would read and re-write data and would try to recover missing data by re-reading the media many times.

For SSDs, they need power periodically to maintain the electrical charge.

Cds, DVDs, and blu-ray don't have either of the magnetic or electrical issues, but still can physically decay over many, many years.

The backup mantra is "two is one, one is none" when it comes to copies of data. Of course the same people who preach it don't necessarily follow that themselves.