When does it make sense to send more inquiries asking about review progress to PLoS ONE?

My paper has been under review for 2.5 months now at PLoS ONE. I am still waiting for the first review result.

I have sent three inquiries to ask about the progress, and all the responses were telling me that the paper is out for review and PLoS ONE is doing their best to process my paper efficiently.

In the title of the PLoS ONE website, it writes "accelerating the publication of peer-reviewed science". I am really disappointed. PLoS ONE is the slowest among all the journals to which I have submitted.

My question is, does it still make sense to send additional inquires about the progress to the journal? If it does, what should I write in the inquiry?