What is the maximum waiting time for I-526 approval?

There is no maximum. You should contact your attorney to make a service request if your case has been pending beyond the current average processing times of 14 months. Your attorney can also discuss other options with you.

There is no maximum. Cases can be pending for two years in some cases, and even longer. USCIS has a backlog of cases, which is the primary reason for delays. Inquiries can be made every 30 days or so, and other actions may be taken to encourage or force a decision.

You or your attorney can call USCIS at 1-800-375-5283, or write to the USCIS immigrant investment email box to make a service request because your case has been out of the processing time.

There is no maximum time under the statute. I have found that if the project enlists the aid of their congressional office, it usually speeds up your application.

I would certainly start inquiring every couple of weeks.

18 months seems to be a threshold time at the moment, but there is no maximum time.

The current normal processing time is about 15 months for the I-526. If it has been more than 30 days beyond the normal processing time, your attorney should be making an inquiry requesting to expedite the case.