I find that Interstate travel can get pretty boring interspersed with periods of heavy tractor trailer excitement especially on a long trip from SC to CT. I’m a bit familiar with your proposed route. Since you have no time limit you might want to try mixing some more scenic 4-lane state highway travel into your route. When I travel from Atlanta to DC I take I-85 to Greensboro and then Hwy-27 to I-66 into DC.
So I your case, I-26 to Columbia, I-77 to Charlotte, I-85 in Greensboro, then Hwy-27. Hwy -27 becomes Hwy-15 for the last miles to I-66. You then can pick up I-81 a bit further west (@30 miles) via I-66. I find this to be is a nice scenic much less stressful route. You do miss a lot of traffic via this route. If you are still feeling a bit adventurous you might consider continuing on Hwy-15 to Harrisburg. I have not traveled further North on Hwy-15 but it can take you around Leesburg and Frederick up to Harrisburg, PA where you can catch I-81. Just a thought…
