The Best DJ In Florida: Excuse me, I never said CDs were useless. Where did that come from?
To answer the last part of your question, I've relied on record pools, several subscription services, as well as store purchases for 30 years. In 1999, changing program format to mp3, nary a CD/DVD has been carried/used in performance since.
Now, using videos, those various audio-only music subscriptions have been canceled and replaced with DVD-video subscriptions. The videos are ripped (or in the latest TM Jones offering, comes already in a mpeg2 format that just can be copied DVD to hard drive), edited, and stored in .vob format on external hard drives. If anything new is not on a video, then my on-line audio-only subscriptions are perused. If not there, then the client will be required to provide it.
My personal experience over the past two or three years is that, as primarily a Wedding specialist here in the North East semi-rural market area, 99% of what was on those music CDs was ineffective, unusable, inappropriate, or flat not danceable, thus a waste of money. At least with video, the guys can watch a little T & A ! (wink wink nudge nudge)
A Houston DJ : Don't you mean a "cache" deposit? Nyuck Nyuck Nyuck.