Irons are not made to last like they used to be - they are also not designed or made to be repairable - in fact the ones I've tried to repair in the past 15 years or so appear to be built to be deliberately dificult to repair.
Unless you bash it about and drop it on the floor there's not much you can do to shorten the life of your iron. Keeping it in its box and never using it is probably all you can do to make it last.
Buy a new iron but don't spend a fortune on it - if you consider a fancy Steam Press Iron the Elna Alize is a good model to investigate - I bought one 2 years ago for £180 but have since given it away to a relative.
http://www.coopersewing.co.uk/home/photos/alize.jpg
Peccavi
August 2009