My theory with rattling is 'do no harm', meaning I will rattle more on a morning hunt than I will on an evening hunt. My theory is that in the morning, I'm not seeing anything, may as well try rattling, and I'll be leaving soon anyway. In the evening I will rattle early on but when it gets closer to sundown, I stay quiet and let the natural deer movement work.
Rattling is not a cure all, it doesn't work every time, in fact I would say less than 20% of the time, but I have had bucks come in slowly, curiously looking, and this year for the first time I had one come charging in looking for the rattling. Never have rattled in a big boy.