The Germany international was part of the Bayern team that won the treble under Heynckes in 2012-13, but whereas the Allianz Arena side have since failed to add another European title to their trophy cabinet, Kroos has lifted the trophy on another two occasions with Real Madrid.
Having also won the World Cup with Germany in 2014, Heynckes thinks it will not get much better for his former pupil and has suggested he might as well call it a day now.
"Toni is 27 and has won the Champions League three times, won the treble with Bayern and lifted the World Cup with Germany," Heynckes was quoted as saying by Sport Bild .
"He should just hang up his boots now...
"Toni is a strategist. He has developed into an even better player at Madrid. He plays like any coach wants his players to play."
Kroos, however, remains hungry for success and has no intention of waving farewell to the game.
"I cannot retire now just because I have won it all," he stressed.
"You always have new goals at Real Madrid and with the German national team.
"I want to win it all."