Many texts describe Heaven's joy as 'infinite' (including a personal favourite, CS Lewis's Weight of Glory') but, as we are finite beings, we must assume this is merely to convey that there is 'a great deal of it' rather than literally INFINITE joy. Likewise many (including plenty on this site) describe that happiness as being 'unimaginably great'. Jonathan Edwards said all joy in this World was but a meager shadow compared to that experienced in Heaven.
What is exageration- how can we tell when something is intended to be taken literally as regards the amount of joy in heaven/the New Earth? As regards Christmas I could say I'm 'dying of excitement' about it, that it is going to be 'ineffibly brilliant'...