3-4 months basically is a new timeline for updates for most bigger games.
Games with some form of gameplay and 2d art take a while since both drawing and programming take significant amount of time relative to writing and posing 3d models. Add in map design, sound effects/music, inventory/clothing systems and debugging and they really take a while.
The VNs with daz models have always been done at 1 month period to fit the patreon model, 2d games that tried to do that model ended up with monthly updates that took 5 mins to complete.
Year from now it will be probably 5-6 months on regular basis.
Depends, you should balance the team/game design so that it wont go that far.
A speedy writer can work on multiple games at the same time while others take care of art like how sierra lee does. If you were to build a team that makes 2d art to satisfy all the written scenes you'd need 2-3 artists full time and someone else to program.
So a big game team would be 1 writer 1 coder, 3 artists + someone with creative vision, and they would produce patches every 3-4 months.