When I was an hourly guy I thought flat rate was stupid and promoted substandard workmanship. When I became flat rate, being a tech was one of the awesomest jobs ever! Well, except when things would slow down. 8 hours for a clutch job? Do it in 2! The only reason your work would be substandard is because you're a substandard working kinda dood. Oh yeah, and warranty is a different story.
Don't be a douche and help the next guy.