How long until a charge is dropped or case is taken further ?

[SummersNearlyOver20]

My son was charged (I think he was charged -he was arrested , questioned with me present & released) with an offence in early 2019 & released pending investigations.
We have heard nothing since & I've tried to search online if there is a time limit on how long ‘pending investigations ‘ can take.
Is it indefinitely?
It just feels like there is a huge cloud hanging over us.
He was a minor at the time.

It doesn't sound like he was charged. If he had been, he would have been given a charge sheet setting out the details of the charges. There would have been a court hearing long ago.

Based on what you say, it sounds like he was released under investigation. Unfortunately, there is no time limit for that. It could be years before he hears the outcome. Sorry.

What was he questioned about?

Unless a very serious offence it is likely to have been concluded but he could contact the investigating officer to ask?

Would all depend on the type of offence he was interviewed for. Minor offences have a 6 month limit, more serious ones can be indefinite. Contact the officer who interviewed him and ask for an update.