It won't last all day/night, more like maybe 7-12 hours(rough estimate)
Hydromorphone is powerful, although it's oral BA sucks, that is, only a fraction is absorbed.
Still, 8mg is roughly equivalent to 20mg oxycodone, although the time release may make it more mellow
If you have "lots of experience" it is unlikely that your tolerance is zero, although you should stay safe and assume it is
Yeah though, if you were truly opioid naive, hydromorphone would almost be to strong to start, however you can take a tablet if you are experienced. Nite that it will take a couple of hours to take effect in CR form, so don't pop a tablet or two, and then take another 40 minutes later cause you barely feel it, lest this turn disastrous
Good luck