First, I've never seen a receiver that let you enter more than one number after the decimal point for a satellite longitude.
Second, the allowable drift of the satellite is probably on the order of the second digit after the decimal point.
Third, unless it's a satellite that I'm on the fringe of receiving (say, SatMex 5), I've never noticed any difference if I'm only .1 degree off, and even then it's hard to distinguish it from variations due to atmospheric conditions, wind, etc.