When a journal displays the “decision in process” status, it means that the editorial board is in the process of making the final decision about your paper. At this stage when the journal decision is in process, the editor will go through the revised manuscript and your replies to the reviewer comments before coming to a decision. The editor might decide to consult the peer reviewers once more. Sometimes, there may be quite a few papers lined up before yours. This is why this stage might take long. There’s no specific time frame for this; the time may vary depending on the journal and the field. I think it would be reasonable to write to the editor to inquire about the status of your paper if you haven’t received a response even a month after the last status change.
I hope this answer helps. I wish you luck with getting published.
You might also be interested in reading the following related articles:
- Why does the status date of a submission change periodically though the status remains unchanged?
- Answers to questions all researchers have about the journal decision-making process
- Tracking your manuscript status in journal submission systems
- How long should I wait for a response from the journal?