What is best practice while designing STAT Accounts in Mass Allocations?

We are going to use Mass Allocation Feature in GL and requires certain STAT Accounts (Natural Accounts) to define. What should be the nature of these accounts? Is it P&L (Expense) or Balance Sheet?

Since if you classify them as P&L, then year after year do we need to define the STAT Journals once again or the balances will carry forward as these are not typical 'ACTUAL' balances ?

Regards

Uday