NTE
Discretion, by it's very nature, is the exception rather than the rule. You cannot 'plan' to work into discretion and you must justify in writing each time you do.
If payment were to be offered as an incentive the whole system would be a mess.
How long do you think it would be before some people 'arranged' to extend a day into discretion to earn an extra bob or 2?
How long do you think it would be before an individual (or indeed crew) chose to work on into discretion, despite being genuinely too fatigued to safely continue, simply because there was a financial 'carrot' being offered?
Let's be absolutely clear, you should only work discretion if:
a. Unforseen circumstances have caused a delay
AND
b. The whole crew are fit and willing to complete the duty
AND
c. The duty can be carried out safely
..........NOT because there is particularly heavy telephone bill that needs paying!