The main risk is that the accrual reversal at invoicing is derived from the posting setup at that moment, not from what was used at receipt. So anything received under the old account and invoiced after the change reverses against the new one — old account keeps a residual that never clears, new account gets an entry with no original behind it. With a large received-not-invoiced population that becomes a reconciliation problem later.
So I wouldn't call it recommended mid-stream. The safer sequence is to invoice down the outstanding receipts as far as you can, make the change at a period boundary, then reconcile the old account and leave it open rather than blocking it so stragglers can still post.
Before any of that though — since you're on service items, is purchase accrual actually hitting the GL today? Depending on how those products are configured the product receipt may not post at all. Worth opening a posted product receipt voucher and checking, because it might make this a much smaller decision than it looks.
Test it in a copy of production with a partially received, partially invoiced PO. That scenario is where this bites.
