Custis died October 27, 1857 and the last of the slaves were freed on December 29, 1862. Slightly more than five years but given all Lee had on his plate then it's perhaps understandable.
Thanks for the correction. I really suspect that General’s Lee actions in signing the manumission papers for the slave at the Arlington estates was an exercise in futility. The Arlington properties had been occupied by Federal troops in late May of 1861. I would think all of the Arlington slaves had walked away from the property sometime after the troops came. As far as the other Custis properties were concerned,
I do not know where they were located. It is possible that some of the 195 slaves that were Lee’s responsibility as the Custis will executor were still slaves in Dec. 1862, provided the property had not been occupied by Union troops.