I guess that depends, Siputgila - Is your rest always so high because you frequently have the game turned off when you could be idling? If so, then even though REST is a good thing, you may be impeding your progress. If you're buying it, then it may not matter. There are a lot of variables.
Valentyne: To prove this to yourself, get yourself a big box of crayons and a sheet of white paper. Now, don't use any of the crayons. What color did you end up with? (I'll bet it ain't black!)