I agree with bedtime bottles being much harder then morning bottles...in the morning you can distract with activity, breakfast, sippy cup, etc...at night, it's quite, there is only a few things to focus on...bottle and bed.
Also, they do know the difference of formula vs milk...Weston will drink milk from a bottle or a sippy cup, but will have NOTHING to do with formula in a sippy cup. He wants his formula in a bottle. And that is what he gets at night. during the day he gets a mix up of formula, milk, juice, water, etc. But in his bottles it's always formula.
I'm thought of switching it up backwards first, but haven't had time to seriously consider the potential consequences yet. By switching backwards, I mean offer him juice, water, etc in a bottle as well as a sippy cup and then eventually see if he'd take formula in a sippy cup...because I think he associates sippy cup with drink and bottle with formula...so if he started to assoc bottle & sippy cup with drink of any kind it might make it easier, but then on the other hand it could make it tougher to wean the bottle, because he's already OK with everything else in the sippy cup.
I think I'll just play it by ear for a while and see if his nipple trick continues. Because if he learns that the nipple trick is not a good choice, then I'm good with a bottle until he's ready to wean himself. I should say he has sooo far weaned himself off everything on his own. Pacifier, breast feeding, etc... so I have HOPE...lol
It's a tough call...I feel if you are both ready, go for it...if you're not do it SLOWLY there's no reason to 'rush' a process that took several months to love.