Not sure if any one has tried it, but thoughts...
With them on High all the time you may have higher current spikes and possibly blowing fuses if your always jumping from static off to full speed...
The life of the fans may drop or fail sooner as they are working at a higher duty cycle for a longer period of time
longer warm up time = longer time of the motor running on a non "optimal" fuel chart
what vehicles are you referring to when "lot of vehicles don't have two speed cooling fans."? Those that don't that I know of have a mechanical clutch fan which is the "low speed" fan....
2001 ZX3 2.0L Zetec-
Hatch Nation #42
Going through Rebuild See "The TICK Build Thread" for details (http://www.focusfanatics.com/forum/showthread.php?t=289168&referrerid=62897)