Warning extremely curtailed over the longest period? (7)

I believe the answer is:

forever

I'm a little stuck... Click here to teach me more about this clue!

'period?' is the definition.
(I know that forever is a type of period)

'warning extremely curtailed' is the wordplay.
'warning' becomes 'fore' (used to warn of airborne balls on a golf course).
'extremely' becomes 'very' (very can mean extremely or considerably).
'curtailed' means to remove the last letter.
'very' with its last letter removed is 'ver'.
'fore'+'ver'='FOREVER'

'over the longest' acts as a link.
I am not very happy about this link. Some or all of it may be part of another bit of the clue.

Can you help me to learn more?

(Other definitions for forever that I've seen before include "continually" , "permanently" , "Eternally" , "always" , "Till hell freezes over" .)

I've seen this clue in The Independent.

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