Best Practice for Changing an PO Charge Account on a Existing PO

Summary:

We are observing a myrid of issues when our end users create a change order and update the acount code on an existing PO line (resulting negative obligations, PO Variance Accounts that differ from the PO Charge Account, challenges processing invoices on updated lines, to name a few). Should end users be creating new lines instead of changing the accounting on an existing line?

Content (required):

I would like to know if others arer allowing accounts to be change or if they are creating new lines when there is a need to change an accound code. The application obviously does support this type of change but it seems like there are other unwanted consequences that we are trying to avoid.