I tend to keep the originals for awhile, and if I don’t go back to them for a bit I’ll delete them. Certainly before I end the session. I do keep original drum tracks though so that I can quickly re-render my drums and just change the instrument in the main drum track, effectively replacing the sample in that track.
I really enjoy rendering something and playing it back on the track I just rendered it from, with all the fx applied still, just to see how it sounds. Rendering something with a dubby delay, then replacing the source with an octave-down rendered sample is sweet.