Baldur's gate 1998- Baldur's Gate II 2000- Baldur's Gate II TOB 2001.
Kotor July 2003- Kotor2 December 2004 (Yes Kotor 2 badly needed more time but plenty here seem to think it's great)
So no you don't need that long when the engine and assets are already in place. While yes it's obvious DA2 needed a lot more time, we can't know for sure that it was just because of the development cycle time and not mismanagement. I mean had they not decided to change the combat style, stylize the graphics and implement a new dialogue system(all to the detriment of DA2 imo) DA2 might of had more time to spend on length(create a credible end game, flesh out characters more) and more locations/dungeons.