We have a few data models we publish that contain the working elements that populate a number of reports. All but one of them are under 1 GB. The data model that is over 1GB is in a Premium workspace. Our primary data model (called "Common Data Model") has had intermittent issues about half of our days over the last 2-3 weeks. Some days it refreshes in 40-50 minutes and some days it will continue to refresh for 2+ hours until it eventually fails around the 3 hour mark (gives us a latency/time out error). Please don't give me some line like "have you looked at optimizing your table structure"...we have done that. If the model itself was a problem, then it wouldn't refresh perfectly fine some days and fail on others. Additionally, on days it fails, I'm able to refresh it on my local in ~1 hour. So there isn't a data element that is failing.
I've had this happen before and the only response I've had that made sense was that "there are too many PowerBI Pro instances using the same resources in PowerBI Service on some days so it ends up failing". I can only surmise that is also what is happening here. If it's something else I can do, I would love to know. But if it's that, Microsoft should enable more resources to that. We pay for the service and I shouldn't have to flip a coin every day as to whether it will work or not.