Is there a value for a single moment of mindfulness (without others) ?
Value, let's face it, is an idea - not to diminish the question. Value can be attributable to all and everything that occurs, whether once and forgotten, or consistently applied. 

All that can be found is mindfulness, whether realized or ignored. No moment, or what appears in it, can possibly have a beneficial or detrimental effect on some other moment, though a clean sink is bliss itself.

If one's present course of practice is intermittent, it is beautiful. If one's present course of practice is consistent, it is beautiful. If we tie our quality of practice to some preferential outcome, there is binding.

If we fail to see or appreciate the fulfillment of things as they are, our very commitment to practice can reinforce the myth that we are somehow less than enlightenment. Presence is awake, this is irrefutable.

Warmly, NightSkySanghaGuy