How about 2 days? though it does not really count as I'm visiting relatives down there too.
And I have my son go pick up the machines as I find them - so not the same. But he does have three of them waiting for me already.
As to how far I'll go without another reason? So far it's been about 3 hours one way. And for the right machine/cabinet at the right price, if I can make it there and back in a day, I'd go for it.
The least amount I've driven is 15 miles - when I found a parlor cabinet in the local quilt shop. It was being used as a display prop, but they were happy to sell it for what I offered.
I live near the middle of nowhere, and most I find are at least an hour away. But then my job is 84 miles away (almost all interstate though) too.
My spouse is worse than I am about this - he loves the machines too and likes road trips more than I do. He's even offered to go by himself for a day to pick up a machine while I'm at work.