Ive rattled many bucks in. Right now is the best time because they are starting to become territorial.
One other thing. If youre going to rattle... RATTLE. If you cant see a deer you cant accurately determine if it works. So, if you choose to do it, do it every 5 minutes. Its just like blind doe calling. Theres gotta be a deer in hearing distance for it to work.
Consider this! You rattle, set the horns/bag down and a big buck out of view was heading in your area. He never heard you. You wait 20 minutes, now wheres the buck, probably back out of hearing range again. You go home thinking... rattling didnt work. Really, you just didnt time it right. If you do it, you gotta commit to doing it. Otherwise you will never really know.