Friends hasn't aged that well for a 90s sitcom.
I would beg to differ on that. Friends is still fresh even though it's first season aired 18 years ago. I don't know whether HIMYM will still be that fresh in 18 years time.
I don't think that the cast of HIMYM has the closeness that the cast of Friends had. The Friends cast were being paid different amounts in season 1 and season 2 before they decided to enter into collective bargaining for equal pay. Jennifer Aniston and David Schwimmer had their pays reduced to match the lowest paid cast members.
I read that Jason Segel plan to leave HIMYM after this season to further his movie career and the cast of HIMYM still get paid different amounts after 8 seasons.