Relatively new brewer here. I have a recipe that says to boil three gallons of the water in a five gallon pot (to create the wort). And then later to add in the remaining water. I bought an eight gallon pot. Can I just boil all five gallons of water to create the wort? Or is that bad?
In short, most early extract recipes work off the concentrated boil process as you have noticed. But if you have the ability to boil AND COOL 5 whole gallons then go for it. Keep in mind one of the main reasons often overlooked for the concentrated boil is to use very cold water or iced water for the other two gallons to get to pitching temps.
You could expect your hop utilization to be a little higher, but not so much so that it will ruin the beer. If you are a hophead then its a win win.
Go for it.