From The Gap back to Bundaberg is around 450kms assuming no major road works or delays that's about 5 and half hours of riding - Even the quickest way to Brisbane is around 360kms that's 4 Hours of riding - So probably go to Brisbane on the Saturday - then ride home on the Sunday is the best choice. Or make a long weekend of it - Ride to Brisbane Friday - Do the Gap - Nebo - Glorious - Fernvale - Brisbane loop and then home on Sunday - So that would be 360 + 360 + 150 = 870 kms vs 360 + 450 = 810kms - but would mean a relaxed ride around Nebo etc and time to admire other bikes etc at cafes and stops and then a nights sleep between big trips. Mmmmmmm something to think about.