How much air loss over time is considered normal / acceptable for a hybrid tire?
Tyres will always lose pressure over time, I would say that for cycle tyres 1-2 psi is closer to the norm for most including me. This is mainly due to the microscopic pores in the tyre/tube which air molecules escape through over time. 

However don't forget that the air in tyres also expands and contracts with temperature, so on colder days tyre pressures will decrease slightly, and vice-versa on warmer days pressures will increase, it is considered that roughly 1-2 psi with every 10 degree increase/decrease in temperature is the norm here. 

Natural deflation also occurs more rapidly the higher the pressure so as you reach a tyres max pressure it will deflate quicker, and thus to keep your tyres at max pressure you'll need to inflate them every couple of days due to the higher pressure loss rate.