Do you grandfather people in when making pricing changes?

Admittedly, I didn't grandfather people in sufficiently in the first product I worked on and it was a mistake. My goal was to better understand the niche who cared about the product the most (the pricing change did help us with this) but we lost customer trust in the process. Moving forward I can see how grandfathering people in is almost always worthwhile. It gives some flexibility to make pricing changes without losing trust from early customers. There's almost always more money to be made from people who aren't users yet - so there's no need to squeeze happy users for what they've got. Grandfathering them in is a way to thank them for their early (and ongoing!) support. What do you think? Do you grandfather in existing users / customers when making pricing changes?