Whats the difference if someone lives a life of sin where he is over lavim and bitul asseys every day of his life for 80 years and lived a life of unimaginable luxury and tranquility and does teshuva at 81 years old. Will his place in olam haba be the same as if he would have done teshuva at 21 years old?
When it says that Hashem rewards the wicked for the little good they do in olam hazeh and punishes the tzadikim for the little wicked they do in olam hazeh- how is this fair for the wicked? Why couldn’t Hashem simply punish the wicked in olam hazeh as well so they will get olam haba?
To answer the first question, he would have sixty years’ fewer mitzvos. If he does complete teshuvah me’iahavah, his aveiros turn to zechuyos, but I still don’t know if that’s equivalent.
As an aside, a life dedicated to the pursuit of decadence is not one of tranquility.
The answer to your second question is that it’s middah k’negged middah. His focus was olam hazeh, so his reward is here.
You are asking two different questions. The first is answered by a Gemara (yes, there is a difference). The second is a classical philosophical/theological conundrum that would take a very long time to answer.