I've never let a kombucha go that long but it should be okay. The acidity of the kombucha should keep anything bad from happening. You might want to try drinking your new batch in small amounts at first and work your way up. I think it would have been okay to use some of the old kombucha for a starter but vinegar works okay too. I have read that you are only supposed to use white vinegar as a starter, but I've used apple cider vinegar with no problems. If you didn't use any of your old kombucha as a starter it may take a longer than normal to brew.