How important is DUR for relief pitchers.

I looked at some previous examples of pitchers with 35-40 STA,  same Splits,pitches...  one with 80 DUR the other with 30 DUR and historically they've racked up 60-70 IP.   Is DUR not as important for a RP? Is the pitcher with the higher DUR not maxing out his potential?

what would the max IP

40 STA, 80 DUR
40 STA, 30 DUR

Is there a multiplier that somebody has been able to figure out?

If you pitch the first guy at a lower pitch count than his stamina, say 15/30 or 30/30, he should be ready to pitch most of the time and be able to log 100+ innings. The second pitcher will need rest even at 15/15 pitch count and is best suited for a closer in save situations role.

DUR influences recovery time from fatigue.  An 80 DUR pitcher will recover something like 75 points of fatigue after a day of rest.  A 30 DUR pitcher will only recover around 28 points of fatigue after a day of rest.  So the 80 guy will be available to pitch a lot more IP's than the 30 guy, depending on how the owner uses him.

If you fine tune your usage of the first guy (ie make him a SuA, 15/30 PC) you might be able to get 150 innings out of him.  That combination of numbers (40 St/ 80 Dur) is relatively rare among pitchers who also have BL numbers in other categories.  The second guy will probably max out around 70 IP.

I once had this guy on my team:
http://whatifsports.com/HBD/Pages/Popups/PlayerProfile.aspx?pid=312948

As you can see, he didn't have numbers quite as good as your guy, but he routinely topped 100 IP and hit 140+ a couple of times.

Hardball Dynasty – Fantasy Baseball Sim Games - Player Profile: Jack Abercrombie

Went for 136 innings this season with 80 DUR/29STA.

Is poor velocity the reason why this guy isnt putting together good stats?
http://www.whatifsports.com/HBD/Pages/Popups/PlayerProfile.aspx?pid=3629964

I'm surprised he's not doing better, especially since Seattle is a pitcher's park, right?  His vL is mediocre, but his gb/fb is excellent and his pitches are solid, which I think would make up for that shortcoming.  I would actually guess that you're leaving him in too long and he's getting toasted by the last batter.  Try lowering his pitch count to something like 20/25 or even 20/30.  I bet you see his ERA drop half a point after that.