You should alow 10 seconds to warm up in cold weather (I can't remember were I heard that). That allows the fluids to move around a bit.
On warm days that are for example 20C+ a very short warm up is all thats needed , perhaps , start , wait 10 or so seconds and then drive off and drive conservativly for another few minutes.
In winter time when its 5C and less the same method can apply but watch the temp gauge and dont use heavy throttle untill it reaches the normal opperating zone.
I tend to idle a little bit longer than I would recomend because as soon as I leave my driveway I enter quite a fast and busy roadway which may require full throttle applications.
But if a person lives in a typical suburban area with low spead roads around them , even in winter time , start up , wait a few minutes and then proceed with gradually increasing loads on the engine untill fully warm.
This should be the nicest on the engine and be a suitable ballance for FE.
FE isnt everything if you rengine wears out in a 3rd of the time , thats not economy.