Long conceded just three goals in six League One games all month and was man of the match in a 0-0 home draw with Leyton Orient.
Long said: "I would not have believed it if someone had asked me in pre-season that I would have played as many games as I have this season but I like to take it in my stride and keep my consistency levels up.
"My ambition this season is to get promotion - I want to get that first before talking about anything else."
Blades boss Danny Wilson added: "George has been brilliant and his temperament is unquestionable.
"He is learning more with every game he plays and goalkeeping coach Darren Ward has done an excellent job with him, his shot-stopping is certainly up there with the best in the country."