Forum:What's the ruling on gaining infinite lifepoints

Let's say i built a deck that contains a combo that lets me gain massive lifepoints to the point where it can reach infinity in one turn. Do i have to state to the opponent that i'm using these life points for a purpose? Can't i say something like "the game is pretty much over, i have infinity life points, try to take me down, and as long as i have more cards than you in my library, i will eventually win"? I'm asking the ruling in every kind of environment: casual, tournament, etc...