Too much of anything is no good. Even Thank yous and sorrys. There is no such think as not being able,to thank someone enough or be remorseful enough. Limitations are an integral part of human life. If exceed, even good things sour.
By being profusely thankful, we might end up subtly belittling the goodness within the other that lead them to the action that we are thanking them for. In other words, it may take away their sense of ownership toward that action. Hence we should limit or appreciation appropriately so the other person can cherish their,own goodness, cleverness, commitment or what ever it is that lead them to the action.
Also a Thank you or sorry should not be given in exchange for action. Action needs to be met with action for true warmth to be felt.
Everything has a measure and helps to know it. And hence that is the single greatest challenge in life. To know the true value of things the way God does