My 12 month extension of a Non-O visa expires on 2nd August and I would like to know how soon before it expires can I apply for another year's extension.

I'm keen to fly home to the UK to see my mother for probably the last time sowould like to go sooner rather than later but I am worried I can't renew it too early and if I leave and can't return before it expires etc...

So how long before it expires can I apply for another extention.

Any reccomedations for avoiding pitfalls in the process.

many thanks in advance.