JL
Welcome to the forum, you might want to have a look at the following FAQ which explain where everything is
Welcome to Benefits and Work In case you are not aware, your real name appears to be showing in the forum, if you want to change this then follow the instructions in the following FAQ
My full name is showing, how can I stop it?
The diary really depends on your problems, if your condition is a fluctuating one then you need to ensure that it covers sufficient time to show the variation, obviously if it is not then you do not need to do this. That said this is a case where longer is usually better, so if it is reasonable for you do so, then continue with the diary until you actually return the form (see below)
You must ensure that the form is returned to the DWP by the date on the letter that accompanied it, failing to do so can result in your claim being closed. So, whilst you should wait as long as possible to include these notes, do not do so if it will compromise your returning the form on time, you can always send the notes on afterwards.
Gordon