On the oceanic checklists it says overhead the waypoint.
Personally, I like to check it if I forgot how much we had 10 mins ago . . . plus,
you can write a "Howgozit?" One of the few things of any practical use from an ATPL course. You can create a Howgozit and laminate it - Thus laminated you can scawl on it and rub off the writing at the end of the flight, using a wet finger. (so as you can use it again)
Its a goer because it gives you, at a glance, exactly how much fuel you have compared to how much fuel you planned to have - thereby determining if you are headlong into the teeth of a jetstream or for leak determination.
They are real handy and can include: PNR points, Critical Points and you can mess them about and make them overtly complicated or just have a simple graph, consisting of a vertical scale in the left margin, a horizontal one at the bottom of the page.
Vertical = Fuel Qty therefore T/O fuel at the top (-RES)
Horizontal= Dist NM. (obviously you have to write in the NM and fuel qty amounts to tally - not just two lines
)
A diagonal line from top of fuel to end of NM scale - (for obvious reasons the Dest should never be zero) and your final fuel will be the amount of RES+ all the other qtys you managed to get away with.
JFA. Just Flying along, at any point on the Dist Horiz line note your position
(D from Dep) and then note your fuel. Stick a little asterix or cross where the Dist and Fuel-on-board intersect - after time, you may see a pattern forming* - more importantly if the little crosses are above the diag line then you are quids in, if the crosses are below the line then you have to ask why this is and by what amount and get your calculator out.
When you become very fast using the calculator then you can progress up to a notepad and pencil
NB: Obviously this is NOT ETOPS planning or equi-time points this is simply a "how much have we got left" based on "distance flown"
*you can determine from the pattern of crosses you drew by a mere glance as to what your fuel situation is going to be in X miles time - or, you can get the ruler out and draw a median line bypassing the crosses in a straight line.