Use the bot tracker https://steembottracker.com/ & monitor from there. Go to "Actions" tab in orange & click on details. The ROI changes as more people put their bids in. As a matter of fact, I think there is some windows where it is profitable, I think when less people are bidding and this is usually when the US is sleeping. Just my guess but at the time of writing this, there are not many profitable bots out there. Oh & by the way, there is a min & max age for the post defined by the bots, usually from 0 mins for some bots & 20 mins for others till a max of about 3 days or so, mostly.