You can tweak your settings to see what works best for you, it may be 3 hours it could be 2. It's different for everyone depending on things like internet speed (which affects how fast you buy items, which can cause more misses), what time you AB and if the shop is restocking.
Here's what I did:
I only ran mine for 2 hours without a break.
When I used 2 hours, I ran Abrosia for about 5-6 hours a day total. (Usually with an hour break in between the next time. So around 3 sessions of 2 hours. I used the scheduler for this). I still managed to get a good amount of items with two hours, and a total run time of 5-6 hours a day. I'd say only running for an hour would be a waste.
Take breaks in between, done by stopping and starting Abrosia. No one sits for a long period of time without needing food, water, or the bathroom. ( usually I waited for around 5-7 minutes after stopping to restart it again.)
Never leave it overnight, no one sits for 24 hours, 12 hours, or 7 hours straight restocking. Abrosia has a scheduler in it, so you can set times for when you want it to start and stop, which minimizes the risk of accidentally leaving it on for too long.
I'd recommend not going over 7 hours a day. People do get bored if they're restocking for long periods of time.
Edited by Satsuki, 26 August 2013 - 05:22 PM.