It's about 50 years old I think. According to this document from DTMR (PDF), bridges now are designed for a nominal design life of 100 years. Assuming that the design life was broadly true in the 1970s (say 70-100 years), I would estimate that it will be good for another 30-50 years at least before either major reconstruction or replacement works are required.I think removing it would be a terrible idea, for the alignment reasons and the traffic flow, it seems nonsensical. But isn't it already 60 years old or so, what is the lifespan of a structure like that?
They would likely need to retain more than just the facades on a few of them. The two buildings next to the Grosvenor (Duncalfe & Co and the Duncalfe/Grosvenor extension) are both locally heritage listed and, unlike the Grosvenor itself, are still relatively intact internally. In addition to these two, the Hillsong Theatre (formerly Lyceum/George/Dendy) and the little red building at 366 George Street (Frankie & George Coffee shop, formerly Pie Face - a remnant of a much larger building) I would like to see all retained in full. The buildings on the Turbot Street corner can definitely go and, given their current state, I'd be ok with the terraced shops between the theatre and red building being replaced - they may be old, but they don't actively resemble their previous state, and would likely require a lot of work to do so.While also keeping the George St facades.
A reminder of what we are getting, looks like to top 3rd of floor plates to go