timing chains and sprockets

[White Anthony <anthony.white@domain.elided>]

Kind Alfisti
 
I was brought up to believe that one should never replace chains without replacing the sprockets they run on.  This was the divine law, passed down long ago by the very Gods of motor-racing (the words were found mysteriously but beautifully machined into the inside of an aluminium alloy sump).  Therefore, in my planned timing chains replacement, I was going to replace both the primary and secondary timing chains, the primary, intermediate and camshaft sprockets, and the chain tensioner.  
 
However, I've just had a Fiat and Alfa mechanic tell me that he's never replaced a the camshaft sprockets on any Alfas, has sometimes replaced the crankshaft sprockets, and has 'once or twice' replaced the intermediate sprocket.  
 
Part of me suspects he told me this because he didn't have the parts, part of me wonders if this was bad practice on his part, and part questions whether I am just being unnecessarily careful.  
 
Has anyone views on the above?
 
Regards,
Anthony
.
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