I'm considering to change my job but worry about if the left H1B days are enough for me to re-apply PERM and I-140.
-Because your I-140 is approved, your h1 has been extended beyond the 6 year limit. So, as long as your current employer does not withdraw the I-140, you can continue to extend your H1 at a 3 years interval. If you do the H1 transfer now, you can get another 3 year term. Then, you can ask your new employer to file PERM/I-140 and the time is much enough for you to do that even if your current employer will withdraw the approvedl I-140 after you change your job.