Quote Originally Posted by Full_Bleed View Post
It lasts 66 seconds.

Personally, I'll just have two sneak macros set up. One that macro's a tensor's cast right before going into sneak and one without. 99% of the time it'll be used before engagement and will cost the assassin about 1 second. Comparing it to scroll healing in combat is silly.
This is exactly my thought. If you are getting ready to engage enemies with high fort saves you are obviously going to take that extra 1 second to scroll tenser's before going into sneak.

I wouldn't contemplate running it all the time, but the situational assassinate + bab bonus is worth the 1 second casting time.