We went one year without getting them back and though we didn't have an issue with our audit per se (we use a volunteer), I found it disconcerting that we didn't have the checks - can't verify they weren't altered, can't look back to verify what they were written for, who signed them.
Our new bank provides check images which is better than nothing (not as good as the real thing, but easier to file, and certainly cheaper for the bank). In evaluating banks, I wouldn't select a bank unless they offered free check imaging. If you want check images, shop around. Banking is very competitive and this is one feature banks compete with.
Is it necessary to have the canceled checks for an audit? Our new bank account does not give them back to you, in fact, I think there's a charge for us to get them.