C172 PLT PERFORMED A TOUCH AND GO TO THE PARALLEL TAXIWAY.

Narrative

THE GND AROUND THE ARPT WAS PATCHY COVERED WITH SNOW -- GIVING IT A MOTTLED LOOK. FEATURES ON THE GND WERE NOT VERY CLR AND DISTINGUISHED (A MINOR CONTRIBUTING FACTOR). ON SHORT FINAL I STARTED TO THINK; 'THIS LOOKS NARROW;' AND I WONDERED IF THERE WAS A DISPLACED THRESHOLD; AND I WAS WONDERING; 'WHY IS THE CTRLINE YELLOW?' I CONTINUED FAT; DUMB AND HAPPY TO A NICE TOUCHDOWN AND TOUCH AND GO ON THE TXWY WHICH PARALLELS RWY 29L. UPON CLBOUT I NOTICED I HADN'T PUSHED IN THE CARB HEAT -- EVEN THOUGH I WENT (MENTALLY) THROUGH TOUCH AND GO CHKLIST. ANOTHER SIGN OF BEING BEHIND THE PLANE AND NOT THINKING. IT WAS ONLY ON DOWNWIND; LOOKING FOR/AT THE RWY FOR MY NEXT TOUCH AND GO THAT I REALIZED I HAD DONE MY LAST ONE ON THE PARALLEL. I THEN DID 2 MORE TOUCH AND GOES ON RWY 29L. I DON'T THINK THE TWR NOTICED; BECAUSE NOTHING WAS SAID. I WAS SURPRISED AT HOW EASILY IT HAPPENED; EVEN WITH THE QUESTIONS COMING TO MIND. SOME FACTORS: LACK OF RECENT EXPERIENCE OVER THE LAST 5 YRS OR SO; BUT THAT'S WHY I WAS UP THERE DOING TOUCH AND GOES. NOT THINKING AHEAD OF THE PLANE OR ABOUT WHAT I SHOULD BE DOING OR SEEING. TERRAIN BLURRED BECAUSE OF SNOW. ALSO; I FLEW A LOT IN ALASKA; AND MANY OF THE STRIPS I LANDED ON UP THERE WERE UNIMPROVED OR SMALL; PAVED STRIPS. THE PARALLEL TXWY LOOKED LIKE LOTS OF RWYS I'VE LANDED ON BEFORE -- IT DIDN'T LOOK OUT OF PLACE TO ME. I JUST FAILED TO SEE/ANTICIPATE A NORMALLY MARKED PAVED RWY RIGHT NEXT TO IT.