My generator is similar to yours. The question is not how long you can run it, but how long could you run at full load. I have run mine to power all my house (but not everything all the time, and I can't use the stove or A/C when on generator). I have run it for days at a time without concern.
Generators are rated as "prime" and "standby". If it's rated at "prime", it can run full load continuously. If it's rated at "standby" (which our consumer devices would be), then it is only rated to put out full load at a fraction of the time (maybe as low as 50%). Most engines are rated to run over 1000 hours, and it really doens't matter if it's continuous or once every couple days as long as it's not abused with lack of oil, poor gas or overheating.
Run Synthetic oil. Less breakdown under that hot piston, but you will REALLY appreciate using it if you EVER have to start it in 'non-ideal' conditions (like it being cold outside).
Sit it where it can get a breeze, or you could even put a small fan pushing air on it to keep it cool if you are really concerned about heat.
Like others said, you should shut it off to refuel. You are just taking chances that something will ignite the gas fumes if you leave it running (and the muffler is hot enough alone to do that)
Also observe the concerns with carbon monoxide poisoning..... all too many fatalities happen with this.
I do check oil each time, but don't usually use much.