Does the Home Office expense have to be taken yearly once it is initially taken? and does it carry forward?

Does the home office expense have to be taken yearly once it has been taken?  Then, does it carry forward if it's lowering a refund?  If one has two schedule C businesses and one is shutdown can one remove the home office and any future accounting when one sells the house in the future?  

 

Also, can one amend last years return to switch to simple from depreciation method? And do any of these increase risk of audit.