When placing a Stalker's Mark at long range, the visual UI element showing how much time is left to teleport appears only after a Mark lands, however, the time it takes for the projectile to land is subtracted from the visual. As a result, the bar empties before the teleport window is over.
For example:
This results in the bar starting with 1 less second on the timer bar, and allows you to teleport up to 1 second after the bar empties.
For example:
Throw projectile ----[1 second]---->Marks targetThis results in the bar starting with 1 less second on the timer bar, and allows you to teleport up to 1 second after the bar empties.