Hey! So I've wondered lately: even among very, very close friends, like practically siblings, is age still a factor in speech/way of addressing one another? Do people care when they're really close? Are people different aged "chingu"?
Although ultimately it boils down to a case by case basis, age is still a factor. Generally, the larger the gap, the more important it is to consider age (and status) in the way you speak to someone.
The larger the age gap, the more formal form of speech should be used.
Even if two people are close, you can't act nor talk to them like they're the same age as you.
You can never use informal language towards an older person unless they say you can.
Yeah, its the sounds I can't seem to get right. If I look up people saying the two to compare, they both sound exactly the same...
Also, for the closeness thing where you don't ever treat someone outside your age group as if they were the same age, would that also apply if they were only 1 year older?
Short of them telling you it's alright, it's safer to stick to polite speech. It's easier to be casual with your behaviour when the age gap is smaller, but polite speech is more about showing respect for someone's age or status than it is about how close you are to the person.
As far as the vowels go, the best way I can think to describe it is that ㅐis a slightly shorter sound than ㅔ. It's not an overly large concern as it's not something that's commonly distinguished in speech.