Yes, you can run your gas fireplace all day if you want to. There is no danger in doing so, and it can provide a very cozy atmosphere in your home. However, there are a few things to keep in mind if you do choose to run your gas fireplace all day. First, be sure that the area around the fireplace is well-ventilated. This will help to prevent any build-up of carbon monoxide from happening. Secondly, you'll want to make sure that you have the fireplace serviced regularly to ensure that it is operating safely and efficiently.