I'm ~14 hours in and on my 5th and final run. First playthrough should be about 5 or 6 hours depending on how quickly you read, how fast you solve the puzzles, and how much you use the fast-forward function.
I'm reading decently fast, solving puzzles on average in 10 minutes or so (about 15-30 min for new ones), and using fast-forward all the way. I should finish the final ending with a total playtime of ~17 or 18 hours, depending on how long the ending is. The last two endings (Endings 1 and 3) are a lot longer than the rest, so I'm taking that time into account.
You should be able to finish by the time the release comes around. Even if you do one room a day, you should be fine. VLR is another case altogether though. I've been hearing estimates of 50 hours to finish the whole game!