Most hikers take 10 to 12 hours to hike to Half Dome and back some take longer. Along the way, you'll see outstanding views of Vernal and Nevada Falls, Liberty Cap, Half Dome, and-from the shoulder and summit-panoramic views of Yosemite Valley and the High Sierra.
Most would say the reward is worth the effort. You will be gaining elevation (for a total of 4,800 feet) most of your way to the top of Half Dome.
The 14- to 16-mile round-trip hike to Half Dome is not for you if you're out of shape or unprepared.