I'm thinking of doing segmented sleep. Basically 1h 30m from 9pm, then 4h 30m from 2am.

I've been reading up on this, but I'm not exactly sure what the difference is between a 4h 30m core and a 5h core. I know that a 5h core is sleeping an extra 30 min beyond a sleep cycle, but I'm not sure what consequences that might have. I'm basing all this on the idea that a core is 1h 30m long.

To be clear, I'm open to sleeping for 5h if it is more beneficial to my health, but I'm wondering if it's actually possible that it will be hindering my sleep quality?

The same goes for 1h 30min core, is there any reason why I shouldn't be sleeping 2h instead?

Am I thinking of this wrong? Is it that core length can vary and more importantly, adapt over time?

Any help greatly appreciated.