If an average guy was put in the middle of an endless crowd of Zombies and given a samurai sword, how long do you think he would last before getting too tired to cut their limbs and heads off?

Conditions:

-These Zombies move really slow, they can not run (so you have a few seconds to rest between each strike)
-They are coming towards you from all directions
-It can be day or night (with lights) but the hot sun or cold weather is not a factor
-The sword is not heavy (light-average weight)
-You are wearing comfortable clothing
-The ground is a flat surface, nowhere to hide (earth not asphalt, and not dry or muddy)
-You are not too thin or too fat, are rested and not hungry, but not too full either (you are carrying some power bars just in case though, 1/50 zombies are carrying Clean bottled water, in case you get thirsty)
-You can only kill them with your sword
-You can use dead zombies to (build a wall, hill etc.) but I’m assuming that is not a good idea…)
-There are no other weapons/equipments you can use/get to. No trees, no buildings to vehicles. Just an endless flat land/eath.
-There is no chopper coming

*If nighttime, the light is not from any source you can reach. (ex. you can not climb a lamp post)