I can go as long as 4-6 hrs.....been as long as 24....but trust me that's pushing me to my utter limit. Two hours I'm comfortable with, and have grown used to it via watching easy child's boys......that's about the timing that the little one is occupied with being fed / napping and nana can slip on the porch for a quick smoke.
Mine IS the hand to mouth, actually more so than the nicotine oddly enough. It replaced nail biting. (imagine I thought I was so smart at the time ugh) Well, mostly replaced it.......I also used sun flower seeds to stop that habit. Then? well, the salt from the seeds make me so ill I had to wean myself off of them. That was as hard as the smoking all by itself, silly as that sounds. Whole hand to mouth habit.
Art classes cured me of it while doing art and crafts. I found I concentrate better without them. Was a hard process though to get used to.
To help cut down, due to budget..........I put off having one after a meal as long as I can, like doing dishes ect. I put off that first one in the morning the same way. Take the "habit" part out of the habit and it's easier for me. Just like I did with smoking in bed or in the middle of the night.