That's what I do too and it works. However, my biggest complain is the sole durability. I had mine for a few months (nowhere near 3 years) and the sole wore out to the point where there was a hole on each shoe on the balls of the feet area and I had to replace them.
I hope this issue gets solved with the new 2010 running models (Bikila, Speed) which have 2 additional millimeters of sole.
Unfortunately Speed is only available in Europe, while Bikila is practically impossible to get anywhere. There was another five fingers shoe made with thicker soles and kangaroo hide, but apparently the stitching on the kangaroo hide is weak so they're having problems with seams splitting easily.
I hope this issue gets solved with the new 2010 running models (Bikila, Speed) which have 2 additional millimeters of sole.