I view the aspect of G day working very simply.
Assuming the maximum effort that one can exert is 100%, I feel that on the days I am rostered to work, I am obliged to perform as well as possible, so I put in 100%.
Sadly that therefore leaves 0% effort available for G days. QED!
For those who do choose to work on G days voluntarily, whilst it is a personal choice, it appears the general consensus is that in the long term it does neither the individual, nor the pilot group as a whole, any long term good.
So look in the shaving mirror after you have picked up the call from crew control and accepted the duty that may give you an out from an undesirable duty or an extra couple of days off, and tell yourself honestly that the individual now removed from said flight who has lost x hours in EFP is inconsequential and the crewing problem will get better now you have 'helped out'.
But you're ok right?