frequency of current DVD image change!

i came to know about http://cdimage.ubuntu.com/dvd/current/ that host current karmic DVD image

it was reffered by a freind of mine and he told me that image doesnt get modified for a fortnight(2 weeks)

i started a download on 21 Aug , half of file was done ......
it was last updated on 18 Aug by site ..... now there should be a fortnight available to download it but to my surprise file was modified on 22 Aug .......

now can i use that 2.5 GB(approx.) data that i have downloaded or do i have to restart the download? are there any other options available ? what is the normal frequency of DVD image update ?

i also thought about using torrent but ..........a torrent file is not provided for karmic...... may be because a quickly modified file is not suitable for torrent!

any help would be appreciated!