I've done it maybe 5 to 6 times. The rewards are soooo bad, the primaries have never dropped for me not once. I have all the elder ciper exotics so SCREW SKOLAS! I'll tell you what I do know, Bungie is soooo douchey they'll wait til TTK patch and be like "we also adjusted the drop rate at Skolas blah blah blah" they did the sh!t with crota after the dark below and I'm bankin they'll do it again here. They know those Skolas and prison in general rewards are garbage, but guess what? We paid for em already jokes on us. Now before they tune prison to be a better encounter they're shoveling TTK info at us for the next big score(by score I mean lining their pockets with consumer mulah). It comes a point and time where you gotta decide to hop off the hamster wheel or keep runnin the endless race