Never sleeping depends on the room temperature, which will affect how hot the hardware will get. If it's really hot, you will want to let it sleep to cool down. Also, running 24/7 means the fans or fan will never stop. This will mean introducing more dust into the computer, as well as possibly burning up the fan motors sooner than would be the case otherwise.
Another aspect of this is if you don't have "Put the hard disk(s) to sleep when possible" in Sys Prefs>Energy Saver, that will mean the drive will be running 24/7. I don't have that checked because I think it puts more stress on the drive to have it cycling off and on constantly. However, I do sleep the computer when not in use. Therefore, my drive, although it isn't sleeping when the computer is being used, isn't running 24/7. Some people think it's good or at least OK to run the drive 24/7, but there is no evidence it is, and although I can't support this with anything more than personal preference, I think running the drive 24/7 can't be too great for it.
A lot of this is just guesswork and personal experience and preferences.