Yes hopefully 10 years +, something to remember is that all earlier Li-Ion chemistries had the longest service life if they are kept around 50% charge and definitely avoiding the combination of high temperatures and high charge levels. Battery developers may have reduced that sensitivity now but I still don't leave my cordless tool batteries at 100% or empty or leave them enclosed in the ute in the sun at any time.
That's very philanthropic of you, if I had spent $18K I would be looking to make a maximum return any way I could. If your energy retailer offered reposit power Tesla would probably only need to offer a software upgrade for you to use it.
