Then again, the stress and melancholy he suffered every year of the Civil War (and which aged his face decades) could have shortened his life.
On Reconstruction, personally I feel that if he didn't have any prolonged total troop occupation as there was (which he may have and may have not), he would have used troops or the militias on a case by case basis whenever and wherever the Southerners threatened or oppressed black civil rights (I believe in its plan, the Southern states were to readmitted if they would follow the US laws and rights for the freed blacks, which enforces my idea on Lincoln using troops to enforce civil rights in some form or another). And I think his idea was to educate the blacks and then give them the vote (I believe they were to be given citizenship before that whole education thing, but I'm not sure), so I'm not sure if you would take that as his policy being educating the blacks while giving them the vote with a Freedmen's School type deal (similar to what the "Radicals" did), or educating them for a short time and then giving them the vote after a short time where he feels they've been taught well enough, or a long term thing of many many years of educating them, and after those many years giving them the vote.
Take into account too that the Southerners were warming up to Lincoln at least to a degree and he was planning to be kind and benevolent toward the South, so that could smooth some bumps in southern reactions to things both in OTL events that would happen (IE, Reconstruction) and ATL events.
And Lincoln's plan was to retire after his second term, and go out to California with Mary and explore the west. So his retirement would be bumbing around San Francisco, maybe a few photo-ops with Mark Twain and Emperor Joseph Norton, maybe seeing the Pacific Northwest, etc.,etc.