I try to limit myself to 3 - one in piecing, one quilting, one binding. However, I have to admit to 2 Block of the Month currently in addition to that. I just finished 2 quilts (ready for quilting), so now I can start my next "big" one. But I'm probably going to jump into a mystery quilt too. I think the most I'm ever actively piecing, aside from BOM and mysteries, would be 2. And the second one is usually just if I need a leader/ender project for a big quilt I'm working on (or bored with). More than that and I start to lose pieces.
Now, having said that - I have a pile of scraps I was just eyeing today. Will you share the pattern/technique that got you inspired?