Using dc motor as a sensor
The result will vary with motor type. Using basic brush and commutator DC motors the stall current will exceed the run current. A well as using current it would be wise to set a maximum run time as a safety backup. 

As a bling operation usually uses either a cord feed or N turns of a rod it is quite simple to fit an end of run sensor, especially with a cod where end markers can be fitted to the cord. This is liable to be a much better solution long term than motor current sensing.