If you intend on applying for a green card you need to stick with the same employer until your I-140 is approved. Just getting there with a single employer can

If you intend on applying for a green card you need to stick with the same employer until your I-140 is approved. Just getting there with a single employer can take years, and if you don't have an approved I-140 when your H1B expires your out of luck. Also up until 2017 even if you had an I-140 you would still lose your spot in line if your employer revoked it.