My 98 KRS is burning 1/2 quart every 600 miles now with 57k on the odo. It runs plenty strong, as strong as my 2000 with 17k miles and with similar compression readings. Worn valve guides are therefore the diagnosis for my 98.
At your oil consumption I’d run her as is.
98 K12RS taxi, 2000 K12RS taxi, 2004 K12GT, 2009 GSA, 2014 R-Nine-T