Sleep requirements
Different people have different sleep requirements. Most people have to sleep 7-8h on Mono (called NSR, normal sleep requirement), people above 8.5h (6 cycles instead of 5) are considered to have an increased sleep requirement (ISR), whereas people at 6.5h or below (4 cycles instead of 5) are considered to have a reduced sleep requirement (RSR). Increased sleep requirements can mean many things, and may even just be due to poor sleep-hygiene. ISR does not necessarily make reducing your sleep unviable, but you will likely have to stick to extended versions of most schedules.How to determine sleep requirement
There are several ways to determine how much sleep you need. One that works for many is to sleep Mono-Recovery, Monophasic sleep with good sleep-hygiene but no alarm. After two or three weeks, or when you're stable, your sleep requirements are how much you're sleeping on this schedule.There's one caveat to this tho: You may sleep much more on MonoRec than your actual requirement, or be unable to hold a consistent mono at all (common with RSR). If you suspect that this is happening, especially if you feel like you're oversleeping the whole time, there's only really one method left:
This other method is: Try it and see. If you can adapt to M3 without a whole lot of trouble for example, you probably have RSR. If you can adapt to M2, you probably don't have ISR, etc.