Adaptation to a sleep schedule usually, takes at least one month. Often, if one is not able to maintain the schedule for an extended period of time, it is not worth attempting a reducing schedule. Whether or not it is worth pursuing an adaptation largely depends on your personal objectives.
It is expected that productivity will be significantly decreased during adaptation, especially during stage 3, which can make it exceptionally difficult to stay awake at certain hours. Depending on the schedule and the person, the effects of tiredness may or may not be noticeable outside of the night and early morning hours. If the tiredness is minimal during the day, it may be possible to stay close to the level of productivity on the original monophasic sleep.
More intense schedules such as E3 and Uberman will cause a drastic decrease in productivity, as microsleeps may appear at any point during the day. Stage 3 is also expected to last longer on these schedules (in the case of Uberman, it may never resolve as the total sleep is too low).
Schedules with multiple sleep blocks can add structure to one's daily life, which may make it more organised and productive. However, the need to prepare for sleeps, especially during adaptation, can be significant and hinder the ability to manage one's time.
Adapting to most schedules would result in more time spent in dark period, which can limit your range of possible activities. If your work depends on the ability to see colours, it is important to consider whether the extra hours will be useful.
In addition, any kind of sleep deprivation is known to reduce self control, which may cause one to become more distracted and less able to focus on work, even when not noticeably sleepy.
Increased episodes of dreaming are often reported during adaptation to different sleep schedules, especially those involving naps in the early morning (e.g. E2 and E3). This is attributed to the increased likelihood to wake up during REM sleep during adaptation, which is particularly likely in naps placed in the REM peak (early morning).
This effect often diminishes as adaptation continues, as light sleep gets inserted after the REM period prior to wake, reducing the likelihood of waking up directly from REM sleep. However, the overall level of dream recall after adaptation may still be higher compared to the original monophasic sleep, though this is highly unpredictable.
If the primary purpose for polyphasic sleep is to explore dreaming, it can be worth the effort to attempt even if the schedule cannot be maintained in the long term.
Compared to an irregular sleep schedule (i.e. Random), any stable and reasonable sleep schedule is better for one's health. During adaptation, schedules with more sleep are less likely to cause detrimental health effects. However, adaptation to reducing sleep schedules incur sleep deprivation, which is undesirable and unhealthy in the long term. Switching schedules often drags out adaptation, which prolongs the effects of sleep deprivation.
Reducing sleep schedules can also be attempted to mitigate the effects of insomnia. For this purpose, it would be worth attempting schedules even if not maintainable long-term, since the adaptation can help build consistent sleep habits.