Dear Gil,
The reason for running the period end function is multi-fold.
Assuming your ledger company profile specifies Clear Transaction Detail by - Period End, use of the function clears paid transactions out of the current transaction files and if historical transactions are being kept for more than zero days (see option in the company profile), moves same to the history file. It can also clear old history out of the history file as well as fully paid retainage details.
Running period end keeps the current transactions file as small as possible which in turn speeds up access to the file.
Another main purpose of the function is to update the Period To Date Statistics. If you have never run period end your PTD statistics are meaningless.
In the event you do decide to start using period end, you will only be able to delete vendors once current transactions are fully paid or adjusted to zero and cleared from the current transactions files. The vendor historical transactions must have also been cleared out of historical transactions prior to attempting to delete the vendor.
You will find this function in Adagio Payables and Receivables.