I find that texting my students at the beginning of the day still gives them enough time to forget their private lessons and intros.
People are creatures of habit and routine and I find a 3 hour reminder works best for them to adapt their routine and make it to their lessons.
(If it's a morning appointment I use a 1 hour reminder.)
For intros I like to email and text the day before as well as a 3 hour reminder on the day of.
If we could schedule our SMS reminders I believe this will help attendance and give Rainmaker the opportunity to sell twice as many SMS credits because to me it's worth it to text twice per intro.