My favorite coaster trips have always been road trips of typically about a weeks length. I would always aim at going to 4 or 5 parks in a 7 day time frame because I find that a few rest days are necessary to remain sane and actually enjoy each destination, especially when doing all that driving. For example I went on a 7 day trip where I drove from Chicago (my hometown), to Toronto (Canada's Wonderland), Montreal (La Ronde), Lake George (Great Escape), NYC (SFGAd), and also hit Cedar Point for a half-day on the way back to Chicago.
I prefer driving simply because I love to be able to have the freedom of my own car (not some cheap base model rental). Obviously some destinations would require flights, but I only opt when truly necessary, I haven't ventured to any parks over seas just yet..
Recently I've also been into "Daycations" where I'll wake up early and go to a park within 4-6 hours away and comeback at night. Being able to stand long car rides is one thing I'm grateful of.