The frequencies and powers of the radiation used in them haven't been in use long enough for us to get decent long-terms studies out of them.
That is because the process of freezing eggs and then successfully warming them and using them to achieve pregnancy has not been in use long enough for most such candidates to have had eggs retrieved in time, usually by the age of 35.
Once any given design has been in use long enough to identify its failure modes, the frequency of follow-up studies can be adjusted accordingly.
Battery life is reportedly up to 6 hours of active (GPS) use — long enough for an average runner to complete a marathon and still have juice to spare. .
Long-term biological effects are unknown at this time because e-cigarettes have not been in widespread use long enough for assessment.
A number of insulin-sensitization agents have recently become available, but only metformin has been in use long enough for reliable conclusions to be drawn regarding its effects on cancer in vivo.
The OE system was only recently deployed in 2011 and results are not yet available, but the EDE system has been in use long enough for preliminary results to be presented.
If CIDA are not perceived as usable or likable in the eyes of the patient, it is unlikely that the technology will remain in use long enough for an evidence-base to be explored and established.
Although most of the research to date has found little link between cell phone use and health effects, there is some concern that cell phones have not been in common use long enough for such effects to be determined through studies.
