I recently learned that there are certain event eggs that you will
miss out on if you don’t have an open space in your party at the
moment that you would have been able to receive them. And I’m
wondering, are there any events that would result in you receiving
more than one egg at once, meaning that you’d need to have multiple
spaces in your party or else lose one or more of them? I guess I’ve
gotten lucky so far not missing out on any event eggs, but will
need to keep one space in my party open from now on, but would one
space being open at all times be enough to not risk missing out on
anything? I’m pretty worried about this now.
just to note that while what BlackReshiram said is true, you should
be careful if you're adopting retro eggs from rumbling, as Pokémon
adopted from the rumble may fill your party first, causing you to
lose the egg