Do not give out false information if you are pulling it out of your butt. You don't need to get an alignment when you change wheels/tires. Hell I would be forking out $1000 a month if I did that (since I change tires every weekend sometimes 4 times in one weekend).

You do need an alignment everytime you change something on your suspension. Lower or raise the car, adjusting camber, etc....

The feathering is usually from too much toe (either out or in). In my opinion if you ask for 0 toe front and back you get better wear and better turn-in without sacrificing skitterish steering. Most tire wear comes from toe not camber.