How long will Ilford DDX stay fresh?

I'm using Ilford DD-X to brew 120 rolls, diluted 1:4 as per the recommendations. Assuming that I'm usually making it up fresh, how many films can I realistically expect to get from a fresh brew before it's time to throw it away and mix up a fresh batch? I haven't noticed much difference in running three or four through a batch, although I'd be the first to admit that my approach to temperature control is somewhat - ahem - relaxed.

Any suggestions??

Thought this title looked familiar.... (there was a url link here which no longer exists)

Dear timd,

The Ilfotec data sheet details how many rolls and how to adjust developing time:

http://www.ilfordphoto.com/Webfiles/20061302032542969.pdf

Neal Wydra