To each his own, but I wouldn't start (let alone fly) an airplane in the winter without first pre-heating. In my view, this is advisable whenever the temperature is below freezing, and an absolute requirement whenever the temperature is minus 7 C. Pre-flight idling is insufficient, and may itself damage the engine.
See further:
(1)
AvWeb;
(2)
F.E. Potts' advice (note this comment: "Mike Busch, the Cessna Pilots Association's engine specialist, claims that one cold start at the lower temperature extremes can cause as much wear as 500 hours of normal cruise operation. This takes into consideration the metal-to-metal contact between the piston and cylinder walls caused by the uneven expansion of the aluminum pistons and steel cylinders as the engine goes rapidly from very cold to very hot");
(3)
Peter Tanis' SAE paper.
On the other hand, see also
this contrary view.