I am in my 8th year H1 (valid until June 2013) with approved I-140 and a priority date of June 2011.I am now offered a Permanent position by my client.Would it be a wise decision to take this offer at this point of time ?. Can you please answer the below

If my client can file my H1 in premium and my Labor immediately in EB2, Will I be in legal valid status even if my employer revokes my H1 and I-140 ? Can I port to my old priority date if my employer revokes I-140?
If I get 3 year H1 with the client and if employer revokes my I140, will the new H1 still be valid and can I continue with my Green card process ?
Do employers usually revoke I-140 and how much time would I have if my employer decides to revoke it ?
Is it more safe to first get my H1 extension with my current employer (probably 3 years) and then take the full time offer ?
In future, if I am laid off by my client, Can I apply another H1 and start my green card process again ?