Newly Married Filing Jointly Primary Residence Questions

(1) We are going to each maintain our primary residences for three or four years until I retire while just visiting back and forth on weekends. Not sure if relevant, but he's already retired so I'm making more money than he is, and both residences are in NC about two hours apart. Whose address should we use on our married filing jointly return? 

(2) After I retire, what if we sell one residence and live together in the other? Can we take a $500K gain exclusion on the one we sell or only $250K?

(3) What if we sell both at the same time and buy something together? Can we take $250K gain exclusion on each residence?

(4) Or to qualify for a gain exclusion would we have to sell one, take the exclusion, then wait two years to sell the other which would then qualify for another gain exclusion? If we wait two years in between, can we take a $500K exclusion on each sale?

Thanks very much!