Well....
1. If you have a good tax professional, he/she also informed you when your taxes expire and furthermore bought you another several months of NOT PAYING THE IRS...pushing your tax liability closer to the expiration date.
2. Your tax professional also might have avoided you a "higher" payment plan that a less skilled tax professional might have put you in.
3. Your tax professional also might have informed you that after a few payments, they could perform a penalty abatement on your tax debt.
4. The installment agreement does prevent the IRS from levying you or garnishing your wages.
5. Your tax professional might have made about 8 phone calls to the IRS over the months- saving you the hold time and grief associated with managing your own tax case.
6. Finally, your tax professional also might have informed you that - you should check in - in about 4 months to see if your financial circumstances have changed - and to see if you might qualify for something better like an Offer in Compromise.