My girl usually strikes shortly after I put the mouse in. She usually likes me to hold it in the air slightly(I had originally been putting it on the floor of the box and moving it around before finding she likes to do the mid air strike).

There was one time where after about 20 minutes she still hadn't struck at the second mouse. I just put her and the mouse back in her tank with the mouse on the enclosure and by morning it was gone.

So yeah, normal is within 1 minute for a strike/constrict. Any longer than that and I'll reheat under the lamp a little more in case she can't sense it and she usually takes it. Beyond 20, I guess she's not hungry at the moment, but she's currently on 2 weanlings until I run out, so I know she'll be hungry later.