Do we have the same sleep cycle every night?

I understand that our sleep cycles change as we age, and that every one seems to have their own sleep habits and requirements (my Dad naturally seems to require about six hours sleep).

My question is, will my sleep cycle be the same every night? I have never been able to pinpoint exactly the start/end of my REM periods so I find it hard to pinpoint exactly when to set my alarm for WBTB etc.and I seem to wake up at slightly different times in the night.

Does the cycle vary depending on time/tiredness, or do we have our own 'fingerprint' sleep cycles?

I believe it will remain somewhat constant as long as your consistent with going to sleep and waking up times.

Your sleep cycle isn't locked to the 24 hour clock as much as it is to your own routine. If you go to bed at the same time every night you should be able to set the same alarm every night. If you go to bed at different times every night you will just have to set a different alarm based on when you went to bed that particular night. Everyone's sleep cycles go in 90 minute intervals. So 4.5 hours would be 3 cycles. Add half an hour to give yourself a chance to fall asleep and you have 5 hours which is when more people do a WBTB. Set an alarm for 5 hours after you go to sleep and see how that works.

Note, your WBTB doesn't have to be exactly at the end of your REM period. It does help with WILD but it isn't necessary. If you do a long enough WBTB your body will reset your REM period anyways. Pay attention to when feel a balance of awareness and sleepiness and then go back to sleep.

As your recall improves and you get used to doing WBTB you will wake yourself up naturally at the end of your REM periods. Probably a few minutes before your alarm was going to go off. Look out for this and you may not need to use alarms at all!

As far as I can remember, my mom usually tells me that our body can adjust easily to a different sleeping schedules. Then the average adult sleeps can be less than 7 hours. But these days a six or seven hours of sleep is already good enough.

I have read that we have different sleeping patterns. Yes, as an adult ,we have the tendency to sleep less than eight hours compared to younger ones.