Another teacher here. I am a reading specialist in an elementary school.
I am perhaps in a better situation than some. We seem to have some really good subs in our district. This is probably because there are many more teachers out there than there are teaching positions, so there are lots of young recent grads who are willing and able to sub. Our subs also get close to $100 per day, but then I live in an area where teachers salaries are good.
If I have to be out and find I've had a substitute who is below par, I report that to my principal. Often, after he checks it out, that sub will not be called again. On the other hand, all subs have to fill out a form letting the principal know whether or not we've left adequate plans and information about the students.
If I know I'm going to be absent in advance I leave very detailed plans, maintaining continuity for the students. If it's an emergency I have a folder of generic sub plans that contain lessons that are still valuable and can be taught in isolation of our on-going instruction/learning. This is a lot easier for me to do as a teacher who sees small groups for short periods of time each day. Much harder for a classroom teacher.
My suggestion to the original poster with complaints about the subs is to discuss it with the teacher in the spirit of both of you wanting what is best for the children. You might even mention that several parents have been discussing this. If she agrees the subs have been less than adequate then she can take it to the principal. If this is not the case, the she is put on alert that parents are aware that her absences are having a major negative impact on student learning. This might cause her to ensure that better plans are left or she might monitor her frequent absences.
Upon retirement we are allowed to cash in unused sick time after 20 years of in-district service. I will, hopefully, have close to 200 days of it when I retire. Unfortunately, I will only have 18 years in the district. I will not be using it up, burning it, as you will, before retirement. I rarely use more than a day or two a year.
What does get me annoyed is the amount of district directed days out of class. We are taken from our classes for test administration, test scoring training, test scoring, in-service training, and whatever else the district deems necessary other than teaching. If I were a parent this is something I would be screaming about.