Hi Westly, welcome... Here's the prescribing information (PI) for Evista  (it's the first listing under Warnings and Precautions on the first page.  Please read the entire pdf, so you'll know about all the side effects.  Also, confirm this with your Dr. and take this information with you to your Dr.

Here's a quote from the PI that explains why you need to discontinue this medication during certain medical situations.  "Venous Thromboembolism: Increased risk of deep vein thrombosis, pulmonary embolism, and retinal vein thrombosis. Discontinue use 72
hours prior to and during prolonged immobilization. (5.1, 6.1)" 

According to the PI, you would stop the medication before, surgery, bed rest, or prolonged air line flights.  You do not have to taper the dose to stop it.

Good luck...