"The work of a coach is limited to five or six years.
"We are already in this time frame but after that, things become more difficult because they create habits and links with the players, which can result in things deteriorating."
He also confirmed that he had been approached both by Portuguese giants Benfica in 2004 and England prior to the last World Cup finals to replace Eriksson when the Swede left after the tournament.
Scolari said: "The English wanted me to sign the contract during the finals but that I start the job after the finals were over. However, that would have a betrayal of the Portuguese.
"It simply wasn't possible. Nobody can sign for one national side and continue to run another.
"It was a difficult choice but I understood that I could not accept it," stated Scolari, who guided Portugal to victory over England on penalties in the World Cup quarter-finals - having knocked them out at the same stage of Euro 2004.
Scolari said he was undecided about his next move and said: "I could stay here, go to another European country or return to Brazil. I just don't know."