At my school they advised me to decide as i went along. if the nav had stressed me out and i wanted a break then say so and we would come back and land and do the rest another time/later on. Similarly if it was going well then continue. As it happened the nav went well (during which the examiner ate his lunch), he then asked if i wanted to continue and took control for 5 mins to give me a break before starting on gen handling. All out it took me 2.6 on the hobbs and i'm glad i did it in one. Best idea is to ask these questions with your examiner in the initial brief and see how you stand - after all this is the time to clarify any points on your mind. Best of luck!
Oh and i did mine in a C152 with 2 big guys in - just make sure your weight and balance is right for your fuel calcs etc!