Sifez
It does rather depend on what you mean by 'endurance'.
For maximum aerodynamic efficiency a conventional wing and tail is actually better than a flying wing. Something along the lines of a high performance glider, however there is no one ideal solution as other factors can have an influence of the design.
The power to fly is however directly proportional to the planes weight so the chosen design may have to be altered so that it gives the best combination of aerodynamics and structural strength to weight. For instance a high performance glider is designed for absolute aerodynamic efficiency as it has to carry little or no disposable payload. To carry a reasonable payload its very high aspect ratio but efficient wings would be at considerable structural disadvantage.
A flying wing does give some structural benefits but it has to compromise a degree of aerodynamic efficiency to achieve aerodynamic stability.
'Endurance' can be a complex subject particularly if you throw in the efficiency of the motor and propeller!
It may be better to take an existing design (built correctly it will fly) and once you have determined its limitations set about designing modifications to it to move towards improving its endurance.