Period when extra long game ends finally (4)

I believe the answer is:

ages

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'period when' is the definition.
I can't tell whether this defines the answer.

'extra long game ends finally' is the wordplay.
'finally' suggests the final letters.
The final letters of 'extra long game ends' are 'AGES'.

Can you help me to learn more?

(Other definitions for ages that I've seen before include "Gets older" , "Grows old like sage" , "Yonks" , "(What seems) a very long time" , "Historic periods or prolonged time" .)

I've seen this clue in The Irish Times.

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