The question was, "Do I think there is an age where it's inappropriate to transition?". The answer, probably not surprisingly, is no. We have to judge our safety and other factors, but all things being equal the best time to transition is when you knew, 2nd best time is now.
Here's why. I think a lot of people think "transition" means a checklist of things, but it's highly individualized and also contextual upon where (and when) you are in life.
So at an early age, before puberty. This is entirely social. Your kid wants different pronouns, name, presentation. As a parent I feel like you'd have to be some kind of monster not to support them.
Let's say for argument's sake that they're actually cis and they feel they need this to be able to be "permitted" to express themselves the way they want to. Let them. Show them a world where presentation != gender, and stand with them if the world tries to bully them for it.
Either way you have a kid who knows you have their back. That you can be trusted with big things in their lives, and that you would never be ashamed of them. As a parent, I consider that a pillar of my duties.
Now you've got a pre-teen, and maybe they're not sure how they want puberty to go. That's a hard choice to make, with long term consequences. But since that we have puberty blockers, you can buy them that time, safely.
Without that, a puberty is coming, wanted or not, and both estrogen and testosterone puberties come with difficult or impossible to reverse effects. When they feel confident, you can then help them get the puberty they want, either by doing nothing, or getting them access to HRT.
If you are a mature minor, or an adult, then these decisions can be entirely in your hands. Many places still have barriers to informed consent, and as a society we can work to ensure that trans health care is not needlessly more rigorous than cis health care.
Given a suitable doctor, a mature minor can just ask for birth control. That's often hormonal in nature. HRT is really just as simple, with additional monitoring to watch for well known signs of complications.
Once you're an adult, well the complications can mount, but they're almost all social and all products of a society that doesn't want queer people to thrive. When you're worried about how you'll pay for treatments, hold a job, keep your family, it's a lot. It can be overwhelming.
Unfortunately that's not on the person transitioning, that's on the rest of us to make space for them, to allow them to feel secure. Even if you don't know any trans people, what are you doing to make your spaces welcoming to everyone, to drive out supremacist ideas?
Honestly, based on my encounters since coming out. Trans people are far more common than I think anyone realizes. We hear about the ones who understand their gender so well that it can be do or die, but I suspect many never hatch out of ignorance.
They don't understand what they're going through or they never have a moment of clarity, and just assume what they experience is the same as their cisgender counterparts. As the world gets safer, as the understanding improves, I think more will realize they have options.
And so how do you want them to feel about you when that moment arrives? When mine did, I worried some, but I felt mostly secure that the people I interacted with would largely accept it, and I could probably manage the strangers.
That's largely born out. I think the vast majority of people close to me didn't feel like they'd been duped or that I was suddenly a stranger to them. The sense I got was most felt that "she just got more Adrian".
I'm nearly 40, and I've met folks who started later still, and they all look amazing, and happy, and themselves.
IT IS NEVER TOO EARLY.
IT IS NEVER TOO LATE.
Whether it's your life, or the life of someone you love, help that life thrive.
@itsaddis And that's how learning that trans people exist and can live happily can make people who had no idea want to transition. Statistically, it can look indistinguishible from a "social contagion", but really, it's just education helping people figure themselves out.
@RileyFaelan Been thinking about it more in broad taxonomy. And I think there are 3 main types. Those who know almost as early as they can speak, those who figure it out when puberty feels wrong, and those of us who don't unless we somehow realize we have options.