Whenever a judge serves as a judge pro tempore the payments for subsistence, lodging, and compensation pursuant to RCW
2.04.250 and
2.06.160 as now or hereafter amended shall be paid only for time actually spent away from the usual residence and abode of such pro tempore judge and only for time actually devoted to sitting on cases heard by such pro tempore judge and for time actually spent in research and preparation of a written opinion prepared and delivered by such pro tempore judge; which time spent shall be evidenced by an affidavit of such judge to be submitted by him or her to the court from which he or she is entitled to receive subsistence, lodging, and compensation for his or her services pursuant to RCW
2.04.250 and
2.06.160 as now or hereafter amended.