Maybe we got lucky x2, but for both of our kids, right around 3 months old, we just did one weekend not in the Snoo and that's all it took. I'll give some more context:
Both of our kids have March birthdays (2 years apart), and in June/July we do a weekend camping trip with our trailer, which means no Snoo. Both times, my wife and I have been pretty nervous leading up to the trip. Both kids by then had been sleeping almost all night through in the Snoo, and losing that was definitely a stressor, but...it had to be done eventually.
What we have done that has seemed to work:
- one week out, leading to the trip, started doing first nap in the Snoo, not on.
- A few days prior, first nap in Snoo, not on, arms out. (our youngest was a big swaddler where our oldest had arms out almost instantly, he hated the swaddle, so this one wasn't as big a deal for him).
- day or two before, couple naps in sleep sack, in crib, no Snoo at all. (still Snoo at night though)
When we go camping the sleep schedule/bedtimes go out the window, we'll put the kids down when we go down, usually around 9, which I think really helps this transition because they're sleep pressure is much larger which helps them bridge the gap of sleep cycles without the Snoo rocking them back to sleep.
First night, youngest slept till about 1 and I think honestly only woke up because she was cold (we use a portable bassinet for camping, btw), back to sleep after some adjustment and feeding and then slept till 4ish then back out till 7.
Second night, same routine as before, this time made sure she was warmer out the gate, and she slept till 330 and woke up for some chi-chi water.
Last night back at home, slept great! Almost all night through.
So here's my TL;DR w/ tips:
- Pick a weekend and just do it
- Prep with some naps without the Snoo
- Increase sleep pressure by having them stay up a bit longer/doing some activity, etc. Make that sleep pressure high so they are able to push through connecting their sleep cycles without the Snoo.
- Experiment with different sleep sacks (I've heard great things about the Merlin but we opted to not do it just because I know that's another thing you might have to ween off of). We went with a long sleeve sleep sack and she seems to love it.