I notice that the old radiators are not efficient anymore, being so loaded with deposits.
I am sure there is a way to take them out, fill them up with an agent that would loosen and dilute the deposits without harming the radiator and then just rinse them out.  Maybe repeat the process and then you have a "new" radiator.  
I think, many of us would be happy with this way of getting a well workingn rad. instead of buying a new one.  This way would be cheaper.  
Any reason why it should not be done?
If yes, what is that agent that would do it?
Zoltan