I have a brick house that has not been painted in 20 years. The front of the house is duller than the other sides of the house in color. How long should exterior brick painting last? Would it be wrong to just paint the front of the house?
You can paint just the front if you wish to freshen up the paint job. Wash the brick first to get rid of dust, etc.
Normally paint lasts for 10 years before needing a new coat. 20 years is a long time for any paint. Your home must have been painted correctly and good paint used. I'm sure it is ready for a new coat of paint.