Guernsey21: Going back to RTV's 120 day deadline.  IMO, regardless of the intended (or amended) schedule, this is how long the bidder's submission must be valid, and potentially represents last possible day in which ISRO can issue a contract before they risk having to restart the entire process, or at least request updated or refreshed bids.

Could even be that a bidder voluntarily keeps his bid valid longer than those 120 days. ;-)