Changing Expense Accruals from Period-End to Perpetual

Hi all.  We are looking at changing Expense Accruals from Period-End to Perpetual Midstream.  First off, can this be done.  Second, what are the implications of doing this midstream.  For example after we have changed the purchasing setting to accrue at receipt, will we still have to run the period-end accrual process at month end's until all current PO's with the original Period-End Setting have been received and matched to invoices.  Any other implications?  Thanks