5 perfect Eevees. What to do?
I have 5 perfect, very low-level Eevees that I've had since forever just doing nothing (maybe prestiging when that was a thing). I have all the vapes , jolties, and flares that I could ever need, a 98 Espeon and a 97 Umbreon. Those last two are useless to me in my gym environment. I'm done with maxing my main set of attackers and defenders and I'm looking for a pet project to work on. Would you take any or all of those perfect Eevees and make an Espeon/Umbreon or would you wait until the next eevolutions come out? Candies are not a problem, and stardust I can just save, I am a patient man. This one is the highest level one.

Answers
Um, all of the Pokemon you listed that surpass the Eeveelutions have a secondary typing.
I know. But as i use those eevoltuions as attackers, i am to decide the matchup and i can avoid a matchup, where the secondary typing is disadvantagious.
It is hard to imagine a realistic (non pure hypothetical) situation, where an eevolution is the better choice.
From my personal point of view, at the moment, i will not put any dust into those eevolutions and push the named alternatives instead.
Espeon is a bit different as it has a quite high attack stat, but it will be strictly surpassed by mewtwo in future.
You don't have any stardust, so just hold off. If you wanted any more of the Gen1 trio, you can do raids to get a specific one until you get good enough IVs. There is not much need for multiple Espeon and Umbreon; maybe Espeon if you are trying to solo Machamp raids. Gen4 Glaceon and Leafeon will probably have some method to control their evolution.
I can tell what I would do:
1. Evolve 2 of them.
If Vape power up in time, I would like to have a 3100+cp vape; in ild days Vape was my fav fighter.
If Flareon power up in time. I'm valor so I developed an afinity for fire types.
If Jolte, nice, you can stay there :). If traiding I will give him to a nice Instinct trainer.
2. Wilk the 3rd for Espeon. Power un in time and hope for lvl 40 for mons available. 3000 cp look nice :).
3. Keep 2 for gen 4 evolutions.
At your stardust levels, I honestly doubt these would ever get powered up or used for much...I suppose this is one of those 100% humblebrag posts with no stardust, but if they are all level 1s, it probably won't amount to much use unless you decide to grind and save dust for them...(which is probably unwise and a waste considering other mons or other legendaries)...
I've powered up a few high IV, low level mons like a Level 2 Chancey to max, Lvl 10 Jolteon to 30, and a Level 4 Machamp to 30+...
They probably shouldn't be transferred, but hard to see a huge need or really any purpose at this point in your game other than taking 5 spots...
Could save, but you're probably better off (due to limited stardust for everyone) evolving high level Eevees for the gen 4 versions.
As I said, I am done with powering up everything else I was interested in, I am too casual to do raids and I've found out I can pretty much do anything I need in this game with an army of Rhydons. All stardust was just spent on a Tyranitar and a shiny Gyarados, but I can rebuild easily. That's why I am asking here, I am talking long term projects :)
I'm not interested in legendaries, like I said, I'm too casual. I'll save for gen 4 versions like you and other people suggested
Do nothing until we find out if they're going to have a Breeding mechanic. 100% Mon's will likely be awesome at that time, even if you have to raise them up to a certain level (say, Level 20).
At the time we learn about Breeding, then I would suggest taking actions to make them more useful as Breeders. Say, if it's easier to get an Esperon by breeding two Esperons, then evolve one to Esperon. Etc.