Never destroy bank statements. If the tax man ever gets his teeth in to you, you will be required to produce copies of them for many years. I speak from experience. I used to keep mine for about six months or maybe a year. But my tax man decided he wanted to see mine for a period of the previous three years.
I have just destroyed a huge heap of my bank statements and invoices/receipts from various cash and carries and other places. They were taking up valuable space and were probably not helping my attic floor. But I still have the last five years worth.
I also have my copies on line as well and never seem to have any trouble getting to them if I want to print any off etc.