We are not in probate,my mothers bank account is her only asset. How long do we need to wait to close her account after taxes?

A Durable Power of Attorney is only effective while the person who granted it is alive. Please contact a local attorney about probating your mother's estate.  It may be that Oregon has a method to probate a small estate which will leave some money for the heirs.  It may be that the cost of probate is higher than the amount in the bank account.