I'm prepared to hear that it's just me.
I'm currently using DPs iron which I've not used that often up to now as we used to have an ironing lady who we can't afford now. It's an old Phillips iron I want to say it's probably about 5-6 years old (or older) and has been stood collecting dust for a good couple of years before me and DP got together as he had a high pressured long hrs job and used to have a lady do his cleaning + ironing once a week and she used her own iron.
To get to the point every time I hang up an ironed shirt as I look at it from a distance I can see lots of little creases, some that can only be seen under certain lights, I make sure to iron properly, use the right temperature and use spray for tough creases and pay attention to iron everything, it all looks crease free yet when I hang them up the creases can be seen! 
I'm not sure what I'm doing wrong, or if it's me or the iron although I can't imagine that an iron gets worse with age?
Has anyone had this happen to them?