Probably best to get them in by the end of this month, as they can take about 3 months to process the claim. Otherwise you have the worry of the award expiring before the decision on the new application is made!
I had our renewal award back a couple of weks ago jammie. I sent it back early thinking they would be a while with it but they only took six weeks (ish).
We've had an increased award and it's abit annoying that they won't pay it now (not due 'til end of Nov). I mean if she deserves it then she deserves it now surely As you say if they reduce they take it straight away.