I would recommend switching at some point.
I have two boys. They were both in home daycares.
The older one was in a daycare much like your daughter's (except for the double negatives). Lots of outdoor time. Some TV in the afternoons. Lots of play. A mixture of very healthy food and some junk. We had him in there, and he enjoyed it, until he was 3.5. Then he got 2 years of preschool before kindergarten. More academic, but still fun. (Warning though he was bored in kindergarten, because not all kids had preschool.)
Kid #2 also home daycare. Play based and fun, slightly more educational. Way healthier food. More qualified teacher, much nicer art and projects. More expensive but definitely worth it. Left him in daycare for 4 years, and he's right now finishing out his 1 year of preschool before kindergarten. I guess technically, he's only getting 10.5 months of preschool. I gather that he was "behind" when he started preschool, because it's a very upper middle class, academic preschool. But by 2/3 of the way through the year, he'd caught up and passed most of the kids. Still lots of outdoor time, but maybe not as much as kid #1.
So I would say that before kindergarten, yes you should switch. When though, that is the question. Advantage of 2 years is that she'll make new friends. Disadvantages, you already know. Advantage of 1 year, she keeps her friends a year. Disadvantage, might be harder to make new friends in a year, if friendships are established in Montessori.
Breaks: one of the things that I liked about home daycare is fewer breaks, and they are scheduled at the beginning of the year. One of the things that I didn't like about Montessori (which we didn't use) is that they have four 4-week breaks.
For kid #1, his preschool had a month-long break in June/July every summer. We would take a vacation for one of the weeks. The rest of the time: one of the teachers at the preschool did a daycare/ preschool at her house for 3 weeks (for pay). Another summer a different teacher's daughter was home from college, and we hired her as a nanny for the week. If you ask around, you may be able to find students/ nannies/ to cover during those weeks. Some areas of the country have camps.
Basically, my husband and I eventually started splitting the days for random days off. Kindergarten will get worse, not better. For years we tried to maintain the illusion of full time jobs, with after school care, no sports, and only choosing summer and winter camps (like YMCA camps) that were full day, 8 to 5 or 6.
Splitting the days means we either
- alternate days off with the kids, or maybe share that with friends
- each work half day for the full week. "Half day" because we have flexible jobs, means we can each work about 5.5 hours, so we need to use less vacation time overall.