With respect to basting...I baste all the way around the shape then knot off and start the next piece. My basting is very 'crude'...it just needs to hold the fabric to the paper. Glue can also be used for this although I have not done this.
As to long pieces of thread...when attaching the various basted pieces, I keep going for as long as my design and/or thread lasts.
Two different elements in my opinion. Maybe I am misunderstanding your question but this is my take.