So your choice is to have waited 3 years for nothing, or wait 3.5 years for something. If the outcome is worth having I'd think the better ROI would be to wait the extra 6 months to get that outcome.... yes patience is a virtue but no one ever said it was easy nor fun. ;-)
There is no ROI. My electric bills average less than ~$60/month so the $30K "investment" takes 500 months or over 40 years to pay back, assuming $0 electric bill, which doesn't happen if you are connected to the grid at all. And I'm told NV Energy these days doesn't buy back excess at all, there is no longer NET metering for new installs. So without being able to spend the night+ entirely on storage, in the middle of the winter, you're going to buy grid power.