1. Books are like old friends. Throwing out a favorite book takes on a similar emotional punch to throwing out photos of your children! This is even true with favorite curriculum books, and you find yourself trying to justify keeping them because "the kids might want to read it again some day!" Yeah, I used the same justification to keep a few of my college textbooks, and I opened a grand total of ONE book ONE time, to look up something in my old Anatomy book to help high school son with a Biology assignment. :)
2. Like human friends, you not only want to keep the old (book) friends, but you always want to make new ones! When you see or hear about a new curriculum for one of the subjects you enjoyed most, you immediately think how great it would be to try it... then you remember "oh yeah, my kids aren't home schooled anymore!" *sigh* Then you watch eagerly for your still-homeschooling friends to talk about it, so you can hear what it's like anyway. ;)
3. Most employers don't recognize your years of homeschooling as work experience. When (and if) you are ready to go back to a paying job, your resume tends to be pretty blank, getting filled in with random "skills" instead of work experience. Granted you probably won't have any "co-workers" to use as references, unless perhaps you were involved in a co-op class with another teacher (and even then most employers probably wouldn't "count" them either). Still, it is rather sad for those of us who are serious about educating our children to have our Careers considered invalid. :( All we can do is put our life's work in the "personal" section of the resume, and hope that we can make it the interview stage, where we can have a chance to talk about our years of homeschool experiences (and how we can use all of that experience to benefit the future potential employer).
4. When you stop, you can feel lost, even sort of abandoned. It's the same as any mid-life "retirement" experience, I suspect. (I know military retirement can be VERY difficult for many people, for example.) After years of being busy almost every day all day, sometimes surrounded by "co-workers" (the community of homeschool moms, piano teachers, etc.) and always with your "clients" (your kids), suddenly you find yourself alone. Your local homeschool community may not welcome you anymore, because you are no longer "one of them." This is especially true if stopping homeschooling coincided with a move--these new people don't know you, and it could be seen as creepy and suspect if you just show up at the park when all the homeschoolers are there, but without children of your own. ;) You still have the house to upkeep, of course, but it is exponentially easier without children at home all day! You may be job hunting too, but this can be a lengthy, discouraging, and extremely frustrating process. Eventually, most ex-homeschoolers will find plenty of things to do with their time. If she doesn't find (or want) a paid job, there are lots of opportunities for volunteer work. There may be grandchildren, or church needs, etc. But the transition can be a bit jarring, and take some time.
5. Homeschooling really becomes a part of you, and you WILL miss it. Every day. :)