B737-700 FLT CREW INITIATES WRONG ARR INTO LAS.

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LAST DAY OF AN EXTENSIVE 3 DAY TRIP. DAY 3 FLEW 3 LEGS ALL IN -300 ACFT. CHANGED PLANES AND FO'S AFTER THIRD LEG. SHOT COMPANY PROCS APCH TO MINIMUMS IN NEXT CITY. RUNNING A LITTLE BEHIND SCHEDULE. FLYING TO LAS; ZLA HANDED US OFF TO LAS VEGAS APCH. AT NO TIME WAS AN ARR GIVEN TO US FROM ZLA. ACCORDING TO OUR FLT PLAN; WE WERE TO FLY THE NEW KEPEC RNAV ARR. WE IN FACT HAD OUT OUR SKEBR RNAV ARR. THE ARRS ARE THE SAME EXCEPT CHANGES START AT LPUMY INTXN. AT CLARR INTXN I HAD ASKED FOR DIRECT POVOC INTXN; TO AVOID THE MOUNTAINS. CTLR THEN ASKED WHAT ARR I WAS GIVEN. I SAID LA DID NOT ISSUE ONE; BUT THOUGHT IT WAS THE SKEBR. SHE SAID NO; NOT USING THAT ONE ANYMORE; FLY THE KEPEC. WE BOTH PULLED OUT OUR KEPEC ARRS. AT THIS TIME WE WERE COMING UP OVER SKEBR INTXN. FO PROGRAMMED THE FMS IT HAD A RTE DISCONTINUITY BTWN KEPEC AND SKEBR INTXN. HE FIXED THAT. AT THIS TIME ACFT WAS OVER SKEBR INTXN. IT TRACKED THE ARR; BUT OVERFLEW SKEBR INTXN BY .1 DME (EST). THE ACFT THEN TURNED L TO JOIN UP TOWARDS KEPEC INTXN. THE CTLR SAW THE TURN BUT DID NOT REALIZE WE WERE INTERCEPTING THE ARR TO KEPEC DUE TO ACFT CORRECTING FOR WINDS. SHE THEN GAVE US A 020 DEG HDG FOR VECTORS TO FINAL FOR RWY 25L. HUMAN FACTORS: SECOND TO LAST LEG OF 3 DAY; NEW FO AND -700; HAD BEEN FLYING A -300 ACFT WITH SAME FO PREVIOUSLY. LAS VEGAS OFTEN CHANGING ARRS. WE SHOULD HAVE TAKEN OUR TIME IN OUR PREVIOUS CITY TO REVIEW THOROUGHLY THE ARR INTO LAS. CORRECT THE SIT: WE SHOULD STATE OUR STAR ARR TO LAS VEGAS APCH ON INITIAL CONTACT.