666888, thanks for your reply!
I did make ask my original question clear enough. I really meant to ask the expiration for the visa stamp on my passport.
Repost original question:
"I am holding US H1-b and will have my canadian green card approved and land in Canada soon. When I come back to US, I want to apply H1-b visa (and H4 for my wife as well, we know we don't have to).
Would like to ask, with canadia permenat residency and Chinese citizenship, how many entries we will be granted and how long the visa will last before expires.(really mean to ask visa stamp on passport here)"