if we’re talking about consecutive time spent, ie one single uninterrupted block of time, then I’d say about 7~8 hours.

one time my ex-girlfriend’s cat managed to get way. we think it was one of the roommates opened the door to the back and wasn’t paying much attention. the cat was sneaky, he would try to dart out all the time

i spent the entire day, basically, walking around the fairly large apartment complex yelling out his name and shaking a bag of treats

a few hours in, my ex had a mental breakdown and gave up thinking any continued searching was hopeless. she really liked the cat and wasn’t taking it well

but i just kept at it. towards the end of the day, around dusk when it was starting to get dark, i heard an exasperated meow behind me and the cat came up running to me. it looked very scared and confused.

we had just moved from one place to another a few hours away. so it was used to be an outside cat but it didn’t know the area whatsoever.

anyhow it actually stopped trying to run out of the house after that, so that was nice