How long do you keep Transaction History for? This is a setting for the number of days, found in the Company Profile. Maybe you just need to set this number larger than you currently have: the maximum is 9999.

As posted already, you probably want to keep history longer than one month or 3 months - a minimum of a year and probably longer.

As there are specific Purge Vendor History and Clear Customer History processes, you don't have to do purge history as part of Period End.