Canada-is it a good option to get your visa stamped here?

Hi friends,

My husband is on H1B visa and his current H1B Visa stamp (previous employer) expires in October 2006
He is planning to go to Canada next month and hoping to get his Visa restamped (based on his current employer I-797). Can he do this ?
Well, we do not have to necessarily do the restamping at Canada only, but he has to make an international travel so as to get his I-94 on the passport(as it was issued only until this may), so we were thinking of getting the stamping done as well.

Basically can you get a restamping before your previous Visa has expired?
Are there any restirctions (like you cannot renew more than 6 months in advance etc)?

Please do share your experiences with visa restamping (I-797) at Canada.

Thanks in advance,
Shalini