ZLA CTLR CONCERNED WITH MULTIPLE 'CLRED TO LAND' VERIFICATIONS AFTER CLRNC HAS ALREADY BEEN ISSUED.

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IT SEEMS THAT DURING THE PAST SEVERAL MONTHS WE HAVE HAD A PROLIFERATION OF PLTS ASKING US TO 'VERIFY WE'RE CLRED TO LAND.' THIS IS CREATING A POTENTIALLY HAZARDOUS SIT. WHEN ACFT CALL ON FINAL APCH; WE AS A RULE; CLR THEM TO LAND WITH APPROPRIATE TFC EXCHANGE IF NECESSARY. THESE SAME ACFT CALL BACK ON A 1 - 1/2 MI FINAL AND CUT OUT OUR OTHER XMISSIONS BECAUSE THEY HAVE FORGOTTEN WHETHER OR NOT THEY ARE CLRED TO LAND. THIS OCCASIONALLY HAPPENS AS WE ARE CLRING THE PRECEDING DEP FOR TKOF (RESULTING IN 'BLOCKED!' AND A POSSIBLE GAR) OR INSTRUCTING THE PRECEDING ARR TO HOLD SHORT OF OR CROSS THE ADJACENT RWY. THIS TAKES US AWAY FROM OUR CONCENTRATION AND EFFICIENCY -- SINCE WE HAVE TO STOP OR INTERRUPT WHAT WE'RE DOING TO RECLR THE ACFT TO LAND -- AND AVOID A GAR. MY SUGGESTION IS FOR ALL PLTS TO HAVE IN THE COCKPIT SOME SORT OF MEMORY AID TO EITHER TURN OVER OR CHK TO REMIND THEM OF THEIR LNDG CLRNC. IT WON'T COMPLETELY ELIMINATE THE PROB; BUT ANY REDUCTION IN FREQ CONGESTION WILL IMPROVE EFFICIENCY AND SAFETY.