I think it's useful to keep key hard copy docs. for mortgage/financial. I have known people who had their computers stolen.

I have also heard of stories of fraudsters who have taken over a person's property title without your knowledge.

And depending on the bank, it depends how long they offer storage of e-bank statements through one's account. There's a limited time period.

For taxation purposes, in Canada one is obligated/safe to keep supporting documentation (this includes medical bills. Yes, we have a different medical system and different very limited tax rules concerning that..) for 7 years. (in federal legislation). A person can be audited at any time during that time by the government tax authorities.

For anyone who is reading this (since this is the open Internet): I worked for a Canadian court and several public sector law organizations as well as for a large accounting firm.

I would be seeking advice directly from government websites/help lines that administer tax, finance legislation in your jurisdiction and offer the most objective information. Infractions of the law, would be reported to these various authorities that required personal income/expense documentation.