I've an electrical insect deter with bottles of perfume that deters insects by evaporating it to the surrounding air using a heat plate:


Since my current room is very large, compared to my former room in my current hostel, and my room at my former hostel, and after reading post of some American member about bugs during the spring, which I don't know if it is true also for the Israeli climate and not only for the climate in the US, I decided to connect it and use it.

Than I noticed that the current bottle of my insect deter have an expiration date (Pictures taken today):


It is really that the expiration date is because like food that gets destroyed and drugs that their effects degrading, that the active material in the bottle degrading as well? Or it is a form of planned obsolescence like the expiration dates on ink cartridges, and that the perfume still performs its function after the exp date is expired?

I'd say your on the right track with the active material degrading, that would make the most sense to me.It probably will become less effective over time.

There is far more then just a perfume in these fills. And because those insects are no joke in many areas, the user has to be made sure what he uses is really performing as it should. That means the thing is not degraded when used. It is not just the main active chemical what may degrade, but also the solvent have not yet evaporated, the knot is not clogged and many moredetails that make the thing work,...

Where it can evaporate to in the sealed bottle (before first opening ?)

Where it can evaporate to in the sealed bottle (before first opening ?)

Diffuse through the plastic material, it is not that perfect seal as many people think...

And the active components are quite long molecules with an exact structure, they tend to degrade alone too.

Some oils penetrate through Plastic but in all cases where i seen that happen, the Plastic becomes noticably oily from the outside. I assume there is nothing like that visible in the unopened bottle seals, and the bottles themselves are often made of Glass

The degradation over time - Assumig it is like any other chemical reaction, it is all about slow degradation - There is no definite date of exponential process change (like in biological processes i.e. food expiration date). The material gradually loses effectiveness and the "cutoff" date was chosen rather arbitrarily, there is no abrupt change in the effectiveness anywhere before or after the date

Some oils penetrate through Plastic but in all cases where i seen that happen, the Plastic becomes noticably oily from the outside. I assume there is nothing like that visible in the unopened bottle seals, and the bottles themselves are often made of Glass

It is not only oils, but mainly the solvents. And these do not keep any traces on the surface, because they readily evaporate out.
And with glass vials the problem could be the seal...

The degradation over time - Assumig it is like any other chemical reaction, it is all about slow degradation - There is no definite date of exponential process change (like in biological processes i.e. food expiration date). The material gradually loses effectiveness and the "cutoff" date was chosen rather arbitrarily, there is no abrupt change in the effectiveness anywhere before or after the date

Well, individual reactions are exponential, but there are more of them (like bacteria growth is exponential, what means till some time their concentration is way below threshold, but then it practically explodes fast). Same if some degradation byproduct is killing it - the thing becomes unusable when it exceeds some limit.
And even with an exponential decay:
The efficiency requires certain concentration of certain component. If this component loose e.g. 20% over the year, they put there 20% extra so there is just the required level even after that year. But this means the efficiency is reached over that year, but not any longer.