I learned spider from another similar thread on this forum about a year ago. It fits it so exactly well that I've taken up the term.
I like having a larger piece so I can visually find it, but pretty much always start with a leader. Yes, it helps keep the threads ends down and it helps start the seam especially with triangle points.
I do mostly strip piecing techniques and usually have lots of little ends from that, those get used a lot for the spiders, but usually just once or twice and then they disappear... the big ones I can find/look for.
And yes, I reuse my spiders until they are positively hairy. The current one actually got grabbed up and trimmed down recently instead of being replaced.