they say on the sale side that they partly dissolve in water. they do comply with the regulations
It is the "partly dissolve in water" part that concerns me. This commonly indicates the use of oil and/or oil extracts. Oil is safe for ingestion (eating and drinking), but is NOT safe for inhalation (breathing and vaping). The tissues in the lungs can not absorb the oil, nor can the oil be expelled; so it just clings to the surface, inhibiting the transfer of oxygen, and trapping other foreign material which can lead to infection and other complications.
Like most things we vape, no one (
including me) knows how much is okay, before we begin risking our health. I am NOT saying "don't vape these flavors" because
I don't know. I am
only suggesting, that you might want to do some additional research, and make your own
informed decision.
the ethanol flavorings i have taste 10 times better than the normal i have and i use half the flavor to make it pop
its a danish company called bolsjehuset that make the flavorings[/QUOTE]
They look like they primarily market to confectioners (candy makers). They appear to be similar to some of the flavor extract manufacturers we have here in the United States; such as McCormick, J.R. Watkins, and LorAnn. They are very well respected, and used, among those in the culinary professions, and even used with some regularity in the early days of vaping. Some, such as LorAnn, still find their occasional place in e-liquid recipes.
However, for the most part, they have fallen out of popularity (because of the excessive use of oil, alcohol, and sugars), for other options/brands, that many felt were better suited to use in vaping. Though this too, in not etched in stone, and open to one's own understanding and personal choice.
i just read a bit more and as i understand it ethanol in e juice is considered safe
Correct; ethanol is considered "acceptable" ("safe" is a word that ECF administration is not a huge fan of; because it starts crossing the boundaries of health & safety claims, and there just hasn't been enough thorough scientific study to say
anything/ingredient is "safe," or "not safe")... and assuming you can keep from setting yourself on fire.

Though ethanol is not particularly thought of as "desirable" because of the perceived "harshness" many find it adds to the vapor.
Further, if you mean "safe" from the standpoint of not being responsible for deforming your O-rings, I would tend to agree with you as well. I still think it has to do with the specific flavors you are using. You mentioned the brand you are using is Bolsjehuset, but you didn't say what specific flavors are causing the damage. That can still shed some light on what is damaging your O-rings.
how long should i let it sit with the top open to let the ethanol evaporate
I was rereading your original post, and I must apologize, I don't think any of us answered this part of your question for you.
The short answer is "it depends."

It depends on how much ethanol is in the mix to begin with, as well as the temperature, and viscosity, of the mix. It can be as short as a couple of hours, to as long as a few days.
The common answer is to leave the new mix
containing ethanol uncovered (mixes that do not contain ethanol rarely benefit from uncovered aging), at room temperature, for 24-48 hours (though mixes containing particularly high amounts of ethanol, and high VG ratios, may take even longer). You
can (doesn't necessarily mean that you
"should") accelerate this by adding gentle warming to the open-top technique. This can shorten the process of evaporation, from a couple of days, to a couple of hours.
By "gentle warming" I mean above room temperature (21C/70F?), and below 50C/120F. The higher the temperature; the faster the ethanol evaporates. Note: this
can also increase the risk of accelerated flavor loss of
certain (citrus, floral, and some fruit note seem to be some of the more susceptible flavors) flavors which contain higher levels of volatile aromatics.
IF you are going to experiment with this method, I
strongly encourage you to do it with minimal amounts to begin with, until you know how it is going to affect the overall flavor profile. It also helps (me at least) to have a second, identical mix, that is NOT treated with heat, made at the same time. This gives me a good baseline to understand how the addition of heat affects
that specific recipe (e.g. my lemon recipes are much more sensitive to heat than my custard recipes; and one lemon is more sensitive than another lemon... and so on

).
Finally; please don't take any of this as "gospel." This is only
my opinion, at
this time, based on my own experience, and research. Others may offer different viewpoints, and they are just as deserving of consideration, as mine.Keep asking questions, do your own research, and read, read, read...