Crickey!
Never thought about this!
Have one of the old Casios in my bag - it has been a trusty comrade for a long time and needs one AA battery per decade.
However that DMS button was always too clumsy for me, so I used to convert everything to minutes in the coprocessor behind the eyeballs.
I will opt for the option of adding one page up and than doing a +3000-180, +4000-240 or +5000-300 which will have me most likely covered most of the time.