What's the goaltending situation looking like-

For how well Boston plays defensively, Thomas really hasn't impressed, his stats are more of a team reflection.  But he is still worth 20+ starts.  Assuming Thomas stays the entire season this year(and does not get traded/waived ect), How much ice time is expected of Rask this year(40-50-60 starts?)?  And is Thomas expected to backup, or is this a time share(40/40 or 50/30)?