Am I correct that you're running 175rpm at about 1.4" diameter? That's about 65sfm.
I'm not familiar with the Kennametals, but I'd consider a coated insert and increasing the sfm up to 130, with deeper cuts. I'd also consider adding roughing tool, and just accepting that you're removing a lot of material and inserts are the price.
Sandvik looks like their GC1125 insert is in the ballpark, so whatever the Kennametal equivalent is....
"Reading" the insert at the end of the cycle should tell volumes about how it's wearing, and tell you if it's a problem with BUE, flank wear, cratering...or whatever, and make adjustments from there.
One problem I see is that you're really pushing the insert...ANY insert, with that long of a cutting cycle. You're cutting upside down for clearing chips? Either lots of coolant or none? (It's counter to my old mindset, but running dry often gives remarkable increases in insert life.....you're taking advantage of the heat...a lesson I still have trouble accepting) .. And if you're not getting chatter, push the insert as deep as you can get away with per pass. Let them flanks earn their keep.