Even that estimate is optimistic. This game has already been around for 5 years and isn't even halfway through the story. Unless it goes full Game of Thrones TV show and cuts massive amount of content just to get to the end, I suspect Irphaeus will be in an actual car accident before this ever finishes.
I know :/ if he would go back to the pace of updates this game started with (1 substantial update every 2-3 months) I'd say he could be done with 1 route in 1-2 years.
The issue is that the more recent updates get bogged down with waaaaay too many pointless details, dialogues or just plain fillers that are unnecessary for the story. Remember the idiotic goose chase to find Yoko's house? It was entirely pointless and annoying without adding anything to the story and could have been skipped entirely or the MC mentions how he struggled to find the place and that Otaku has failed him yet again and makes a snarky remark about it (like always) after he arrives at Yoko's house.
Same thing with the honeybee event, there was absolutely no need to present the event in such detail, a montage with some funny highlights interspersed with the different h-scenes would have been way better imho and instead of all the filler we could have had the different girls as options for the final scene and without the blueballs ending of course (another shitty development in recent updates).