The protections at Hogwarts were not easy to recast. Every Headmaster's portrait had reminded him of that after Professor Flitwick had told Dumbledore that several protections had been dropped. He had to admit that he'd been a little lax in maintaining some of those protections, trusting his charms master to do most of the maintenance. That being said, he was pretty certain that he was dealing with the incredible fertility of a Weasley boy for why the broom closet protections were down. After all, Arthur Weasley had been responsible for a similar problem at the end of his seventh year. Dumbledore felt it was his great luck that Bill and Charlie hadn't knocked them down during their time at Hogwarts.
Most of the protections and charms of Hogwarts held up extremely well over the years. He'd had to reset the Grand Staircases last year, after the pattern ran out, but that happened every hundred and nineteen years. He wouldn't have to do that again as headmaster, and was pretty sure that his next five successors or so wouldn't either.
The problems with the house protections on the girls dorms had been solved with the application of a few fresh runes. The old ones had worn off just a bit. The broom closet protection system, however, was being rather annoying still. The protection was linked in a spider web between broom closets that had not been well documented. Dumbledore was having a hard time finding exactly where the trouble was, as the errors cascading throughout the closets kept bringing the protections down.
At the moment he was on the floor in the thirteenth broom closet he'd dealt with this morning alone trying to find any runes that might have been placed incorrectly. Properly done the broom closet should create a magical field that made both the girls and boys who went into it infertile for twenty-six hours. Most of the time it was still doing that, but there was a pulse jumping through the network that was reversing that for two minutes and forty-nine seconds every twenty-six hours, actually making the couple more fertile for that time. Hogwarts had been very lucky that only four seventh-year couples had been caught by the pulse.
If only the problem had been on a twenty-four hour schedule and the reversal was when every student was supposed to be in bed. Dumbledore sneezed, blowing some dust off the floor of the particular closet and revealing some runes he hadn't seen before. There was the timer. He ruthlessly removed it, replacing it with a constant. Then casting a test he discovered that he'd caught it when the protections were down. He groaned, and stripped the broom closet out of the network. Hopefully the other closets would be up and he'd only have to redo all the runes in one closet.