you can probably just do it as a seperate state! make a sprite with eyes closed and sipping, and set that as a closed/open mouth and just switch with hotkeys whenever you're sippi
Someone gave you an idea already but! There is a way, if you set the blinking as a gif, it will last as long as the gif does! So you can create a gif that has a specific length that you want and use that to decide how long you want the blink time to last :]