the age of the aircraft is largely irrelevant. Governed and audited maintenance programs are thorough enough, providing they are adhered to. As far as the client is concerned, they only raise comments if the interior is looking old and tired. Put a new interior in a 1979 Hawker 700 and the client will say nowt.
I happily use Hawker 750's aircraft and will continue to do so.
We find more and more we are asked about age of aircraft; from our US clients in the main. It seems as though many think an aircraft 10 yrs.> is more likely to fall out the sky. Crew hours and experience I consider more relevant; 2000 hours on type between a flight crew is more important than if the aircraft was built within the last 10 years. If the mx. programme is adhered to, where's the rub?