Consumer Buying Decision Process

The consumer buying decision process is a five-stage purchase decision process that inlcudes problem recognition, information search, evaluation of alternatives, purchase and postpurchase evaluation. Everyone experiences problem recognition. It's when a buyer becomes aware of a difference between a desired state and an actual condition. For example I have a calculater that I use for all of my classes, but one of my classes requires a financial calculater, so I had to go out and buy a new calcualter to meet my actual condition.
Information search is the next stage. After one recognizes the need and or problem, the buyer then searches for product information that will satisfy the need. When I learned I needed a financial calculater I asked my teacher about the brands, then went for the cheapest one. Evaluation of alternatives is the third stage and states that a successful information search yields a group of brands that a buyer views as possible alternatives for possible purchase. Reading up on brands and customer reviews can help narrow your list and give you the best brand for your product.
The fourth stage is purchase and this is when the consumer chooses the product and buys it. The last stage is postpurchase evalutaion and this is something that everyone experiences. Maybe you buy something you have been wanting for a long time but it's expensive and you have bills to pay for. But then one day you buy it anyways and after you buy it you start to regret it and wish you never purchased it. This is called cognitive dissonance and I know personally I have experienced it many times. I love what I'm buying at the time but in a day or two I wonder why I every bought it.

Is there a time when you experienced cognitive dissonance after purchasing something? In order to avoid this feeling of cognitive dissonance should we think and do more research before buying a product? Is there to much impulse buying going on? What do you think about consumers and their spending habits?