To be honest I am a bit confused on this point – the manual says that “media that have to be created from scratch” (things that have to be rendered) need recompressing. But I always have this option deselected. I always render to the current settings (with or without things being rendered in the timeline) and I never noticed a problem.
NB I forgot to mention a few things:
– in the Video Processing tab of the Sequence settings you should switch to 10-bits processing, if you want to take advantage of those 2 extra bits.
– what is convenient about sequences that are set to 8- or 10-bits uncompressed is that you will have more filters available in real time.