PSA!!! if youre not gonna everstone your eevees, DON'T BUY THEM AS PETS!
don't get me wrong, many eeveelutions make incredibly loyal companions in the right hands. eevees are extremely sensitive to their environment, and may evolve spontaneously. This means that one night outside could mean a whole new responsibility you may not be prepared for.
oftentimes a family gets a cute eevee and think they dont need to everstone it because it isn't being battle trained, and end up in the emergency room because their newly evolved umbreon just spat venom into their eyes.
you can be the most careful owner possible and your eevee could still dig up a thunder stone in the backyard, bask in the moonlight for a little too long, or tackle a grubbin a little too hard near a mossy rock!
most shelters can't take in pokemon that are destructive, and most eevees who have spontaneously evolved are unprepared to handle their newfound powers. I've unfortunately had to box so many surrenders of stressed eevees because it just isn't safe for the other pokemon in our facility, and I dont have the time to work with them all.
soo many house eeveelutions are abandoned each year, all because of an issue that is easily preventable. while most pokemon can be released in the wild without issues, most eevees that come from breeders have known nothing but indoor life. house leafeons in particular struggle with self-pruning and can't take care of themselves in the wild. there have even been cases of wildfires resulting in major habitat loss caused by abandoned flareons!
all this can be prevented by just... handing an everstone to your eevee. I understand that everstones are pricey, but it is so worth it to save yourself and your eevee that stress in the future. there's a common misconception that its cruel to everstone your pokemon, but its entirely reversable. It essentially gives you and your friend the time to decide what, or if evolution is right for you.
if you can't everstone, minncinos, lillipups and rockruffs make incredible companion pokemon, and continue being good companions through their natural evolutions.
TL;DR everstone your darn eevees!