I don't think the casts mind working one extra half hour a week. It is just like doing a one hour drama. The workload is not that heavy. And unlike most other sitcoms, Friends have 6 stars instead of 1 or 2.
Plus, then NBC can afford $ 600,000 salary or even more the casts request.
Don't forget the Law and Order, SUV is as popular as the Law and Order. NBC should seriously think about it. Make it the lead of Must-see-TV-Tuesday!