I140 validity after PD is current

[RIKB]

Company A filed my I140 in EB3 category and was approved in Sep 2010. I left the company and US in April 2012. Company A never revoked or withdrew my I140 till today so it should be in valid state. Now I am planning to reenter US with new H1B from company B based on Company A's I140 approval. Company B will eventually file a new PERM for me and I plan to reuse my old priority date. But all this will take some and the rate at which EB3 PD is progressing, I feel my date will be current very soon. So my question is whether there is any time-frame by which I can reuse my old priority date after it becomes current? 
Example - if Company A's PD becomes current in 2019 and company B's I140 gets approved in 2021 can I still reuse that date. I heard that after PD is current we have to take action within one year or it gets invalidated - Is that a correct statement?

[rohit369]

There is no timeframe to use the PD. It all depends on the day on which you are ready to apply for your I-485. The PD has to be current. There are instances where the PD has retrogressed depending on the availability of GCs.

You have 2 options:

1. Start the process with the new employer from the scratch, you get to keep the PD. Here you can now upgrade and get everything done in EB2. Maybe by the time you get your I-140, EB2's PD maybe current.
2. Join employer A and you will not have to redo anything and just wait until PD is current.