I have a Dell Precision M4700 for work that is used for over 8 hours a day working on large coding and 3D modelling projects (My main work machine), It's been faultless for the last 2 years I think it is. I also use an Alienware X11-R2 that is sometimes used for games but is operational for at least 15 hours a day, Both on Win7 both work fine.
