Actually, not significant in total acres measured, as the drift, error, or whatever you want to call it will the same direction all the way around, whether it's as much as your 10-15 feet or less. That is why you hear of light bars advertising "pass to pass" accuracy being higher than a "return point" accuracy. The same principle applies when measuring boundaries, do the whole thing on the same trip.

I have done a lot of this over the years, with cheap handhelds, CF GPS in a PDA, and more expensive external antennas. I have tens of thousands of acres of boundaries saved and archived over many years. In later years with returns for soil sampling, planted crop measurements, whatever, the return position is surprisingly close, and the planted area is closer.