I've been quilting for a little over a year and I have done all my own - first straight-line machine quilting, then muscling the quilt in my little Janome to get squares and outlines, and finally FMQ! the largest I have quilted is probably 5'x7'.
What I have learned is (1) match my design ideas to my ability to quilt and (2) quilting takes time. Most of my problems have been getting fancy designs I can't execute nicely, and being impatient to hurry it along so I can give it to whomever. Those 3 little words "quilt as desired" can result in just as much work as creating the quilt top does! My most recent quilt has SID, outline tracing squares, FMQ leaves and trefoil motif to match the fabric motifs, and wavy lines which follow the cable border stripe.
Maybe next time I will just meander little wave-curls around the quilt like a fancy mattress pad and be done with it!