Assange didn't spend seven years "confined" in the Ecuadoran embassy
He was there willingly, and could have left at any time. For the seven years he was there and the four years he's spent in a UK jail if he'd faced his charges worst case he'd be out in six years from now - if he had two maximum 10 year sentences served consecutively (which is unlikely, federal sentencing guidelines result in almost no one getting the maximum they are eligible for) and federal inmates serve at most 85% of their sentence (i.e. 17 years) with the "good time" deduction (I'm assuming he wouldn't be starting prison riots etc. so he'd be eligible for the full good time deduction)
Not sure how the law works but the time he spends in UK custody awaiting extradition would probably be deducted from his federal sentence meaning his worst case release would be two years from now.
Regardless of how fair you think the whole situation is, he's handled it in a monumentally stupid way and may well end up serving more time in "confinement" hiding/fighting the extradition than he ever will in a US prison. And the joke would really be on him if he's found innocent and it turns out it was all for nothing.