If the maximum sentence is 150 years, but Biden would settle for keeping him locked up another 4 years (so that he doesn't interfere with the 2024 election), then the naive thing to do would be to grant a 146 year reduction of his sentence, but this could end up with Assange serving a sentence of negative length if the judge hands him a sentence less than the maximum.
More seriously, I wonder if Assange's time spent in prison in the UK fighting extradition to the US (after his punishment for skipping bail was served) will count as time served towards whatever sentence he is given in the US. If so, he may only need to drag out the appeals process for another couple of years and the US will have punished him more through the process of him proving his innocence than the sentence he is being threatened with if guilty.