I have no idea why they wait so long. Probably because we are lagging behind on this topic in the UK.
Well, where to start with the list!!!
Slow weight gain and inefficient feeding as a baby (had never even heard of tongue tie, and nobody ever thought to look) I was lucky though, it was never painful, really terrible sleeping with bouts of apnoea, although probably not enough to be diagnosed with it IYSWIM, mouth breathing (high palate encroaches on nostril space) and enormous tonsils, congestion and hearing loss and ear infections (high palate encroaches on eustacian tube space), fussy eating, reflux appeared age 5yo but suspect he'd had it longer, allergies and intolerances (not directly connected to ties, but tied kids are often allergic).
Dental problems are evident now, but as I said in the previous post, we are having them seen to, but without it, he was heading for long face syndrome from mouth breathing, and multiple extraction in his teens. He will probably still need fixed braces, but hopefully not for as long as without his current treatment.
There are also other things that are common in tied kids, but they don't know for sure why. There is a suggestion that the incorrect swallowing action means that the vagus nerve is incorrectly stimulated which could have quite a lot of implication. DS1 seemed to have some sort of sensory issue, although never enough to have a diagnosis - he couldn't tolerate certain clothes (still hates them now), would hate to wear a hat, he had problems with certain textures of food, although there would have been mechanical aspect to that as well because he couldn't swallow properly.
Anyway, we had his first revision done when he was 6yo. It stopped the gastric problems immediately. I later realised that despite it costing ££££ and being done by a tongue tie "expert" it wasn't bloody well done properly at all. We went to see the dentist who trained with Dr Kotlow and he lasered an upper lip tie and posterior tongue tie.
It was about a year ago now, and DS1 says he is glad that we had it done because he feels he can move his tongue a lot better and it isn't sore if he moves it too much. His lip tie is gone too which was annoying him I think. Before revision, if he opened his mouth wide, I could see his tonsils in their entirety. Now, I can't see them at all, I would need a tongue depressor. That illustrates how much higher his tongue now sits at the back of his mouth.
It is a really complex subject, and is very far reaching. Ties can affect the whole body. DS1 has curvature in his neck, possibly from the tensions caused by the ties, and that of course has a knock on effect on the hips which were out of line which made one ankle roll in the way and the other out the way. Basically knocking his whole body out of alignment. Luckily, our orthodontist specialises in this type of thing and completely understands the effects of ties. He is also an osteopath and has been working on straightening ds1 out.
Sorry for the essay! It's just that I could ramble on about this all day 
I hope it's helpful!