This may work, but will likely cause your system to become insecure. Your passwords will be stored in an unencypted manner, and could be accessed without your knowledge.
Another answer in this question suggests disabling the autologin feature of Ubuntu - this achieves the desired result of preventing the system from asking for a password often, yet maintins a higher level of security.
Start the 'Passwords and Keys' program by opening the dash, and typing passwords.
Then right-click the first choice in the left menu, "Login".
Choose "Change Password".
Enter your current password, then press return (twice) to use a blank password.
The system will give you a warning about storing passwords unencrypted.