They have been diving for hours, and need to be fully alert all the time every dive. They cannot do that if sleep deprived, it would risk everyone's lives
^^ This. Diving is surprisingly tiring, even when its serene pootling about in lovely clear calm water. Here they are fighting currents and squeezing through gaps.
There's also the decompression issue. Most of the diving isn't deep, so might not be limiting, but they need to recover from that. The escape diagram includes a '30 metre' section suggesting they have to dive to 30 metres, which does have issues when diving repeatedly.
Also, how fast can they fill all these air cylinders they need? I've seen pictures of hundreds of cylinders and l imagine they have brought in loads of compressors if there wasn't an existing facility locally, but sorting thay would have taken time and needs a good power supply.
Then they have to reassemble kit and resupply all the underwater air stations, which could take time by more divers, who also need to rest and recover, additional to those accompanying the boys out. This takes time and is risky in itself, as demonstrated by the poor man who died doing this.
Hopefully everything will go to plan and the water in the caves won't rise past what they can cope with, but even if it does, it might take another couple of days to get everyone out and just hoping hoping hoping that the mission is 100% successful.