I cant my bow to about 1:00. Sometimes more, sometimes less. It just depends on the circumstances of the shot. LBR is right, when you cant the bow, your head should be canted at the same angle. It helps to keep everything in line and the arrow under the eye.

As to a change in accuracy, you could be doing something different in the mechanics of the shot. Something like gripping the bow differently will change point of impact, because gripping too tightly can cause torque in the bow and one bow I shot would twist in my hand if I didn't grip it well. Other things, like a change in your draw length, a slightly different anchor, a slightly different release and so on can all affect where the arrow will hit. As you found out, changing the cant of the bow also affects where an arrow will impact. Which can cause a problem in hunting situations where canting the bow more or less than you normally do is required to make the shot and you havn't practiced it.

I found that as I matured both in body (getting old) and length of time shooting, that my style changed. Sometimes for the good and sometimes not. They weren't big changes, but changes non the less and when my shooting suffers, I reevaluate my form and make the necessary changes to bring my accuracy back to a somewhat consistent level.

Shooting a stick w/string is a lifelong endeavor. The longer we shoot, the more we learn and the lessons just seem to keep on coming. No one, not even the greats of the sport have all the answers, so don't kick yourself too hard. The longer you shoot that bow of yours, the better friends you will become and the more you will experiment with it to learn just exactly what will happen if you do this or do that. The important thing is that you have a ton of fun with it. Otherwise, it's just another job.

Make em sharp and shoot em straight, or leave em home.