What exactly is your point here? The fact that I used the term 'repellent' as a casual descriptor, or are you challenging the basis of the article? If it's the latter, comparing two commercially available 'chemicals' (does that meet your approval?) to test their effectiveness against the bed bug...
Maidinbham - The linked to EPA article that was cited is relevant in the context of the point that was being discussed - safety of DEET in relation to skin and clothing.
DEET is generally regarded as safe for skin contact, indeed that is its main design intention (it is used to mask human sweat), see the link provided by dougfitz. All your other points are valid.
A repellent placed under the bed posts won't do much for bugs already present in the mattress...
Actually, the 94% figure refers to the percentage of bed bugs that the DEET prevents from crossing the treated area.
In answer to the original question, the article states that 25% DEET should last for 21 days, after which its effectiveness significantly drops:
"Longevity tests of 25% DEET...
Dear Pilgrims,
Please see the attached article (2013) detailing scientifically validated experiments testing the effectiveness of different commercially available repellents against the common bed bug.
In short (and against the received wisdom on this forum that permethrin is most effective)...
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