Some (most?) Luso rates are with limited kms. Your trip could be quite long. Did you check that your rental is for unlimited kms?

Also, Luso does not allow cars taken out of Portugal unless you state so up front and pay extra. I know your itinerary does not mention crossing border, but Marvão is close to Spain and you could be tempted to cross the border. Don't do that with a Luso car unless you have the right paperwork up front.