Indeed, according to TSHOSW, Obi-wan was originally to be about 30 years old in TPM, making him in his 70s in SW. It seems Qui-gon's addition is the mother of all retcons, after all :\
JEDIT: Nope! According to the "Timeline of galactic history", the OT is set 32 years after TPM, making Obi-wan about 60 years old in SW.