How do you distinguish between impulse buys and thoughtful purchases?

When purchases are based on offers and not important for daily use. When procurement is necessary and for daily use

(i distinguish between them by one of the tow we need it urgent (impulse

  but the other one wew neeed it later on not now 

The level of purchase involvement of the purchaser or customer for instance the time taken to purchase or make a purchase decision, questions or inquiries asked or forwarded & interactions between purchaser & seller, level of knowledge displayed about the product by the purchaser etc. Thanks for the invitation