On Mon, 19 Mar 2007 07:41:56 -0400, "Joseph Meehan"
wrote:

It you can keep it from drying (it need not be wet)
longer is better. In some applications it takes years to reach full
strength.

They told me in 1971 that the locks of the Panama Canal were still
getting harder after about 70 years.

Commercially they often spray on a paint like material to retard
evaporation or use plastic.