The 29-year-old scored twice as Italy easily beat Northern Ireland 3-0 to end their Group C campaign unbeaten.
Cassano has played an important role in Italy's qualifying campaign and it took him just 21 minutes to open the scoring against Nigel Worthington's men. A cheeky through ball from Daniele De Rossi played Cassano in and he let the ball drop over his right shoulder before volleying home from eight yards.
His second goal on 53 minutes was equally impressive as he drilled the ball into the net from 20 yards out.
"I've been in the national team for 10 years but I've only got 25 caps," the AC Milan player told Rai Sport. "I'm always in and out (of the national team)." Cassano told Rai Sport.
"I feel fine, now I want to continue in the Italy team. Three years, I want to have three great seasons. Then I can stop.
"I want three more good years and then that's it because if I continue beyond that, it will become a routine and routine stresses me."
"I think I will play football for only that time, have a good Euro 2012 finals and a good World Cup, then at the age of 33 call it a day so I can enjoy my family,
"After the 2014 World Cup? That is my idea, I want to leave when the time is right. "
Cassano also thanked Italy coach Cesare Prandelli for standing by him after an incident earlier in the qualifying campaign which saw the AC Milan forward heavily criticised for insulting a journalist.
"I have to thank Prandelli, he gave me a helping hand when I had everyone against me. I am thankful to him," he said.
"Prandelli has given me so much confidence and told me he believed in me. He has been very close to me at the time when I was struggling.
"He has also helped me to get off to a good start with Milan this season. We have a fantastic rapport, a special one, and I want to thank him for that."
"When I retire, you [the media] can have fun with Mario Balotelli. He is another good character for you."
Italy added a third and final goal against Northern Ireland through a Conor McLaughlin own-goal.
Italy finished their qualifying campaign top of C with 26 points from 10 games.