pitot heat question

Coming back from Mammoth this past Sunday and flying through a snow
cloud West of the Sierras, I had the Pitot freeze over. I realized it
was frozen when I tried to correct for altitude gained in turbulence
and the airspeed indication didn't increase even as I pushed the nose
down and could hear the relative wind increase. Not a big problem -- I
could see where I was going on the AI, and a minute or less after I
turned Pitot heat on, ASI returned to normal.

This did raise a question -- is there a good reason Pitot heat isn't
on all the time? It doesn't seem to be a big power drain, and unlike
carb heat does not to my knowledge affect performance. Is there a
reason I shouldn't turn it on when I put transponder on ALT and turn
it off when I shut down electrics before engine shutdown?

Ari.

--
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