dd2 had an adenotonsillectomy aged 25 months - and definitely needed it. She had moderate to severe sleep apnoea, and was starting to refuse food (other than liquids), and lose weight. She looked like a spider with black circles under her eyes, and when the ENT consultant heard her breathing asleep (we filmed it on dh's phone) he booked her in immediately.
She also had a floppy larynx, which added to the severity of it all, but the main culprit were the tonsils and adenoids.
She never, ever had tonsillitis (thank goodness).
It went fine, even though (due to the larynx issue) she had to spend a night in HDU as a precaution. She was in a fair amount of pain for a week afterwards, which we stayed on top of with 24 hour pain meds - and lost a bit more weight. But her breathing was better immediately, and once she recovered from the pain and GA, she caught up with weight and everything else and is now - aged 5.5 - absolutely thriving.
It changed her life, and ours, for the better 