Air Conditioning - Portable air conditioner question

I purchase and returned a portable a/c because the reservoir filled up in 2-3 hrs and as you know, they shut off when full. This does not help when I need to keep a room cool around the clock.

I'm having trouble finding info on just how long these units should run before filling and shutting off. I'm guessing it should be much longer.

Does anyone know if that quicky reservoir fillup was standard operation or perhaps a malfunction? I bought it a Home Depot and no one there knew anything about it.

Thanks for any input!
------
Edit: I need a portable because the room has windows on only one side and it's the front, window units not allowed. The portable venting is not a problem.

I'm going to assume that your portable has a single duct to the window. If yes, then yes this could be normal if your relative humidity inside is high. This is why I always recommend two-duct models to people that need portable units.

A two-duct model uses one duct to draw in outside air for cooling the condensing unit and the second duct to exhaust this hot air back outside. The two-duct models also include a condensate pump that sprays the condensate onto the condenser coil which helps to cool the condenser and also evaporates the condensate and blowing it outside with the exhaust air.

When the condensate pump on my two-duct portable failed to run it would fill the condensate tank and shut off in a couple of hours, since I fixed the condensate pump it runs for days without accumulating even a half-cup of water.

It was a single duct. But I think I may have another solution. If I set up a pretty lattice of some sort in front of that window, it would hide a window unit and I can get one for that small room a lot cheaper than a dual duct portable.
I'm on my way to look for lattice! Thanks for responding.