@crjlover. same with us.
you know how it is:
heavy ops and/or suddenly ending important ebay auctions.
and before you can say knife you´ll get the fls :O

a very nice discussion ,
the cfmu hand book is clear and you have to update your fpl in 15mn after eobt for all ifps zone .
a little problem still existing is when we loop a CTOT and the aircraft is ready whthin 5 minutes more than the window -5/+10 +10 we can a great delay and passenger are o/b and it will be problem for both the company and atc and parking , sometimes we get new big ctot 10 mn before taxiing . ...

but i ve seen the cfmu book and i ve liked this paragraph:

Can I ‘freeze’ my slot?

No. However, if the CTOT received is acceptable,
then a DLA message should be sent to IFPS using
the following formula :New EOBT must not be later
than CTOTminus taxitime minus 10 minutes.
Example : EOBT 1000, CTOT 1100, but the flight
cannot go off blocks until 1025. The taxitime is 15 minutes.
Calculation :1100 – 15, minus 10 = 1035.
The new EOBT must be earlier than 1035,in order not to
trigger a revised CTOT.