My PERM was certified in August. Took a little over 16 months because it went to audit. Timelines on PERM shot up around the same time as I applied and have been steadily getting worse.
Filed I-485 in November, approved in 4 months and a week. So once your date comes up, they seem to be moving quickly.
I'm now backlogged until October which never used to happen at all to ROW (rest of world excluding India and China) applicants.