Are these two additions, for past lives and future lives, respectively, sufficient to keep active healing in motion to forestall effects from feasible new occurrences among past and future lifetimes looping back to current life? In other words, does one extension in both directions stay ahead of future developments adequately, so we don’t need a future extension of the future extensions?

Yes, the latter is not necessary as you presumed. Having seen that this will add a significant new coverage in both directions, you were wondering how far does this go and how many iterations might be needed, as one can begin to conjure up layers on layers on layers and so on. But we can give you reassurance here that one such extension to take into account past lifetimes and their future unfoldment, and one extension to encompass the future lives and their future extensions in continuing beyond the current moment and represent an ongoing potential for crosstalk, will be sufficient, and further extensions added to extensions will not be necessary.