Do you think it would be premature to replace a 40 year old iron septic tank if it is still doing the job and not showing any danger signs?

If it ain't broke, don't fix it.

If you are cleaning it on a regular bases and have no problems, let it stay.

Chuck

If it ain't broke don't fix it! Why go to the expense of replacing a tank that's doing its job? You must have a reason for asking this question, Would you care to share? Back to you, Tom