I got in a discussion with one of my collegues. This is the context , we are currently implementing the timestamp (in minutes) plugin in the DTM, we made our tests, and now we are correctly collecting the time (in minutes) on a data element. Our conundrum now, is to get to know where do we put this inforrmation. I naturally though of a prop, since this will be launched in every hit, thus not needing any persistance capability. I also added that entry values and exit values could give us valuable information.
My collegues advice was another, they adviced using an evar so we can get the last value (of the timestamp ) when a conversion (any success event) is done. I argued that since the timestamp is being launched in all of our rules ( so all of our hits ), we could still use the prop since the success event and prop would be correlated ( in the same hit ) - but ok lets go with the last value for conversions.
We ended up accepting each others pros and cons, and finished by setting up a prop and an evar.
I would set the value to prop. If the prop is being set on every single hit (which it is as you mentioned), then you can easily break it down by any success event anyways. Having a time variable in an eVar is waste of eVar. As you can see in the documentation, getTimeParting the method used is again a prop and not an eVar.