360 Cambelt Tension Procedure

Installed new tensioners, updated bolts and bearings during cambelt change. Followed WSM to the letter and gap and tension are all within spec after two engine rotations and a 2-3 min wait before taking readings. As time elapses beyond that the left side tension readings start to drop including the gap as the tensioner cylinder retreats somewhat. Is this normal? Are the readings considered good only after the two revolutions and 2 min wait or are they to remain constant indefinitely without starting the engine?