Change employer after I140 approval?

[silverdunes]

Hi everyone,

Following are my status details:

1) I am in my 6th year of H1B

2) My I140 is approved

3) My PD is Jan 2011

4) Will be filing my H1 extension

I would like to know can change employer after getting H1b extension and will the number of years extended persist with H1 transfer?

Can I keep my PD?

Can my cuurent employer cancel my I140? Will it affect my H1b with new employer?

I know this would be very common question, but searching web yielded with unclear answers.

Appreciate all your help.