Your enquiry has been passed on to us here at the Diageo archive from Joanne at Whisky.com
We have bottles the same as your 8 YO Dufftown Glenlivet in our historic bottle collection which are dated c.1980s, however you will be pleased to hear that I have found evidence of this bottle being marketed as early as 1978. This particular bottle continuted to be maketed into the 80s and I have found examples as late as 1985, so from the evidence I have, your bottle will have been purchased sometime between 1978 and 1985. Therefore it could well be 30 years old.
I hope this information is of help.
If you have any further questions, please do not hesitate to contact me.
@JoJo: Thank you very much for helping me. The bottle is probably as old as me. I will enjoy the whisky