I thought I'd encourage those of you who are either in the beginning or middle of the process by updating about my positive experience so far.
I've had my top arch IA for 15 weeks in total (I have to admit that it could have been about 12 weeks but I had a few days here and there that couldn't wear it) The last week was actually unnecessary as I was only waiting for the clear retainer to be ready, although I still had a persistent tooth that needed just a tiny last push which was achieved with the clear retainer.
The results are quite incredible. I am very pleased with the whole process and although it's been difficult at times I'm very happy with my new completely aligned top teeth

Second phase has now started and I've been wearing my bottom IA for a week while still wearing the clear retainer for my top teeth. I also have an expander that I need to adjust every three days in order to make some room for my crowded teeth to been pushed forward.
This first week is being quite more difficult than my experience with the top one. The reason is the expander in my IA which is quite big and takes a lot of space under my tongue. Lots of saliva being produced at the moment and having some difficulty to forget about it but I'm very slowly getting used to it. I have to admit it's worse than the IA only with no expander, though. The speech is better than it was with top IA but I have a bit of pain when I talk as my tongue is quite restricted in terms of movement.
I'm hoping it is true that bottom teeth move quicker and also that I can stop wearing both retainer and IA soon. The plan is to use a new clear aligner for my top teeth to close a tiny gap between two teeth and then go for the fixed wire retainer for good.
Sorry about the long message. I will leave before and after photos soon when I go to my next appointment.
Good luck!