How safe is aluminum wiring in a 1970's houses?

I have lived in a house with aluminum wiring for 20 year and had to replace most of the outlets. The problem is not the wiring as much as the connection in the outlet (copper to aluminum) they make special outlets and connectors to work with aluminum wiring. The cost of rewiring your home will exceed the return when you sell. By the way a home with aluminum wiring has a 67% higher chance of fire then one with copper wire. Also check to see if it also has a Federal Pacific box, they are also a fire harzad