Timing is no longer an issue and guess work is totally illuminated. The down side is you don't know if you are going to have grubs or not. It's very similar to insurance. If you have it, you won't need it. If you don't have it, you will need it.
Bottom line is, preventative protection is much cheaper then replacing the turf.
If you see damage, use a curative insecticide. If there is no visible damage then use a preventative program.