DLA Renewal Help Please

I have just received an application form to renew my DLA which is due to run out in Feb.2012. My last award was for 2 years. I was very relieved at the time to get the award of higher rate mobility and care without a medical but rather puzzeled why the award was for only 2 years.
As I am 66 and have very long term conditions which at my age are very unlikely to improve and infact have got worse since, why can't one be left alone by them ? The stress that was caused by completing the last application form , made both my wife and myself ill. Thanks to Benefits and Works my wife completed a very very full application form which took hours and hours of thought and research, but was successful and ran to many extra pages in answer to each question.
My poor wife is now faced with a similar task again I suppose, she said it was the most difficult thing that she had ever had to complete !! This was despite the advice from the local benefits advisor from the Citizens Advice Bureau who told us to make the answers very short, without including too many extra pages in answer to the questions !!
Can anyone with experience of renewing a DLA claim advise me if it is possible to include some copies of the extra paperwork that we included with the last application, as so much hasn't changed really in such a short time. It would certainly help, or should it all be totally new.
I did note in the FAQ that it is not a good idea to send it back too soon before the old award runs out !!
I wish I didn't need to renew it, but the extra money has made such a difference to the quality of our lives in the last 18mths, especially as our only income is a basic state pension now.
Any advice or experiences would be appreciated.
Cheers Terry

Thanks for your reply Gordon !!
At least we do have some time to compile all the evidence etc. to submit with the renewal form.
I was hoping not to put such a burden on my wife this time, as she has enough to cope with daily, just in looking after me.
However I supose it is going to be a case of repeating much of what we said last time and elaborating on it.
We really wouldn't have had a clue last time without all the advice from Benefits and Work .
Having to go through every detail of ones daily life and how ones disabilities affect one, in such minute detail really does make life seem very depressing and is so upsetting.
Thanks Terry