And if you don't know any of the ways and have to keep reading the description/survey, it can take a bit longer...Which route are you going?
If you follow the Bar Pot Alternative it's about 90 minutes to the New Hensler's connection.
I'd then say a steady hour to get to Mud Hensler's and a steady 20 to get to the main chamber.
From there if you go to South Passage and South East passage back to South East aven it's 30 minutes
Derigging and getting up the pitches is probably 90 minutes.
If you add in seeing West Chamber, the Blowhole, Hensler's Master Cave, Diss last pitch chamber, staring at the main chamber waterfall or down South East Pot, Mud Hole, Sand Cavern, then add on some time. And if you choose Bar Pot not Small Mammal cut an hour off.
In my view GG is a national treasure and all trips should be savoured rather than rushed. maybe that is because I am still undercaved and on the bulbous side.