People now get one to two hours less sleep each night, on average, compared to 60 years ago. A primary reason for this is the proliferation of electronics, which also allows us to work (and play) later than ever before.
The Internal Revenue Service requires that individuals be able to produce records proving any income, deductions or credit claimed for at least three years from the date of a return, the statute of limitations for how long the I.R.S. has to assess additional tax if all income was reported correctly.
If your business has been audited in the past, you should keep all records, regardless of what kind, for seven years. It is smart to have business invoices safely organized and stored for seven years in case they are ever needed as evidence of business purchases, etc.