I understand it’s more than clothes but other than presenting (hair,clothes,shoes,make up,etc) a certain way and having certain interests (either stereotypically girl or boy interests) it does come down to ‘feeling like a man/woman’.
In terms of 18 year olds knowing their minds on this, I’m sure most 18 year olds would say they know their minds on most things! Many 18 year olds swear blind they never want kids, want a certain career, will do x,y.z for the rest of their lives, would never, ever do x,y.z etc etc. 18 year olds are also (generally speaking) not the best at being able to wait - they want everything now! and probably don’t have the best insight into the future.
I know if I had to live my life now based on the decisions I made at 18 I don’t think it would be the best. I’m guessing most people would be the same as that’s the nature of 18 year olds!
Luckily most of the decisions we make at 18 aren’t completely life changing and potentially extremely harmful.
Yes, you have to take on a case by case basis but this won’t stop lots of these children and young adults having their fertility taken away and other complications when they aren’t in the best place or at the best period of their lives to make such completely life altering decisions.
Even if they remain trans forever and remain happy not having the opportunity to have biological children, the affects of the medication is still potentially horrific.
As a parent of an 18 year old who wants to go ahead there is literally nothing you can do but I do feel so many of these children and young adults are being massively let down by the system. A lot of trans children/teens are led to believe they can actually change sex which is so unfair on them.
As for time to change their minds along the way, I’m not sure this is the best way to look at it as it’s not actually ‘changing your mind’. If you feel desperately unhappy with being a boy/girl and long to be the opposite sex more than anything, it’s not about ‘changing your mind’. A better approach may be to say that feeling like this is common/normal, yes it’s utterly horrendous and no, you probably won’t decide to ‘change your mind’ but there is a good chance (this is where statistics should be helpful) that you will get to say, 25 (again would need statistics for age,etc) and feel content as a man/woman.
‘Lots of time to change your mind’ is actually a false safety net as it gives the impression that trans kids going through this did have plenty of time to change their minds and the fact they didn’t must mean this decision is right for them.