well you do...it is called the bobbin...all you have to know is how many yards of thread on the bobbin, then can convert yds into feet and feet into miles...
what machines really need is something that tells you how many HOURS you have on it...it needs, cleaned and timed according the hours of use! Especially the newer machines that you do not oil, but they have the lubricant in them. That goes away after sew many hours of use and only repairman can re-lube it properly!