I think most sewing machine warranties cover just one year in terms of both parts and work. After that, they usually cover just parts for awhile longer (not sure how much longer -- maybe 4 more years?).
The way I look at it, how many machines require warranty work their first year? Especially if a well-known brand. After that, unless the part is a computerized mother board or something along those lines, the parts cost of getting a repair tends to be less than the technician's cost.
I believe the odds are in favor of not worrying about warranty.
Here is a thread I found on Babylocks that covers some opinions about buying an extended warranty:
http://sewing.patternreview.com/Sewi...ns/topic/78746