If you do not store your razors in the shower while not in use, the razors usually last about 2 months. Each cartridge pack comes with at least 4 razor blades. Definitely worth the extra money. They last long and do the best job at getting and keeping that smooth feel.
If you clean it and dry it and store it OUT of the shower, the blades can last for months! Proper care makes them stay in good, working order for a long time so that you can get your money's worth out of them!