Many times, slaves ran away from the Washington's, to have freedom. George Washington owned a little less than half of all of the slaves in Mount Vernon, some successful, most not. The only good thing I can see from this, is that George stated in his will, that the slaves are to be emancipated upon the death of Martha Washington, they cannot be sold again or passed along. Terrible times of America indeed, there was no excuse for slavery.
Old news but why would the first President be any different from any other who followed? Leaning towards the social norms of a given time it is to be expected that those in power and who make the laws often consider themselves to be above those laws. President Washington was no exemption to the normative rule when it came to location of residence and possession of slaves.
Yes, I believe that President Washington cycled his slaves in and out to circumvent the six-month law, because people follow technicalities all the time. One of the black marks on American history is that many of the founding fathers had slaves. These are the same people that wrote about freedom and natural rights. Washington only technically followed the law in order to get what he wanted.
There is some solid evidence to support this. Washington was not exactly against slavery. He may not have been a vocal supporter of it, but he certainly would have done what he needed to (or what he thought he needed to) in order to keep his plantation from going bankrupt.