lot of people do similar. For a skeeter pee (
Skeeterpee -) that is the recomended method for making it, although it is only a 1 reuse.
The only problem with just dumping on the juice on old yeast is that over time, you get more and more yeast and eventually they begin to dominate the flavor. You end up witha 'starter' instead of a cider. I'm not sure where the proper pitch rate or reuse for ciders, or how much should be reused, maybe a cup of the yeast and throw out the rest? Something to think about.