Usually for me, for short to medium breaks, 1/2 the length of the break is spent getting back to pre-break levels. So, for a month, 2 weeks.
That being said, that's for maximal strength, endurance takes a bit longer.
Correct. I've noticed the same. Two weeks for a month off with not much difference in size either.
I like taking a month off or slightly more to travel, and I enjoy the break.
But I do try and eat relatively healthy, keep the calories up and have meals with moderate protein and stay active with lots of walking etc, so get back lean and fit as well.