Total rec days is the average number of days hunted multiplied by the number of hunters. That number does two things for you, it tells you about the season-long pressure the animals receive and you can kind of figure an average days per harvest also.
Me personally, I'm a stat geek, and have recently (wish I would have done it last year) devised a spreadsheet that utilizes the DOWs info, combined with some pain staking measurements, and calculations to come up with "underhunted" units. Then I have a ranking system to narrow down the best units. But that's just me. And I hunt one or two different units every year for deer or elk. Previously, I had looked at the DOW stats like success and population sizes, but that isn't the complete picture.
To me, success rates are misleading and are more of an indication of the amount of private land, except when you get into areas that are more than 80% public land. Then I think success rates are nice to look at, but then only as an average of the last several years, which also allows you to figure out the best season to hunt a certain unit.
But you asked a better question, and that's how do you know when it's time to try somewhere else? That's a very tough question. I live on the front range, and have looked at the stats and harvest management plans for my local units and don't like what I see. But I have the chance to get to know these places much better than I do on the West Slope. Even though I've only hunted my local units a little bit, I still know them better than any other unit I have hunted because I frequently take small half day hikes into my local mountains. To get to the West Slope units whose stats are much more appealing, takes too much time to do frequently. So, when I weigh how well I know my local area with how poor the odds and populations are, I feel I can do better by going elsewhere. My decision isn't as difficult as yours, you're in an area that's not stellar, but is closer to average for the state. But you've also got no one to help show you the local hot spots and are inexperienced with elk, so going somewhere new might not help because you don't have the experiences to draw on to help identify a good spot within a new area.
If I were you, I'd probably stick close, so I could truly learn every huntable spot inside and out. You know the elk are there, but you don't know where ythey go et. You're going to have to either ask questions of the locals or figure it out yourself. But remember, in the summer time, every little opening just off the road looks great, but will have hunter orange at every corner in the fall. You need to envision where the pressure will be coming from and how you can take advantage of it by positioning yourself somewhere or get into unpressured areas. This is where "map time" pays for itself by saving you some boot leather, but it will also force you to look at more and more places. However, elk will not be in the same places in October or November as you find them in July and August.