I do all of the above. According to a former coworker, a sewing factory supervisor, your chair should sit high enough so that you can work at your machine without the shoulders raising. My chair doesn't go high enough for that so I have a cheap bed pillow on the "secretary" chair.
It is hard to take a break when on a fun roll quilting with specialty threads. Keep a big mug of ice water handy and a hubby/friend with magic hands close.