I have only been quilting a couple of years and was working part time so did not get to quilt that much. Now that I have finally retired again (I retired once before from full time and then went to part time work) I am doing more quilting and more researching how to's. I have mostly 50 wt. cotton bought from Connecting Threads but recently have been trying polyester. I have been reading all the info from Superior Threads and they do such a good job of educating that I plan to buy most of my thread from them in the future. I use a 90/14 needle for both 50 and 40 wt and I have a Bernina. Seems to work. I do use the little white teflon ring in my bobbin case and that seems to make the bobbin thread move very well whether I am piecing or FMQ. I have lately used 70 wt poly for quilting/FMQ a tote bag and it worked very well. I think we are learning all the time and have to keep trying different things to see what works for us and our machine.