Farming Science: Obsidian Orbs (+ Question)

In a recent update, there has been an addition that completely changed the theoretically ideal farming setup. I'm talking about the obsidian hoe and orbs.

The problem with these items is, that there is no longer a clear limit on how many plots you can have. Every orb adds one more plot, but the orbs get progressively more expensive. While the first orb ist only 10,000 carrots, your 5th orb is already 160,000 carrots and your tenth orb will set you back 5,120,000 carrots.

I was wondering where to stop buying these, since it is obvious that the later orbs are far too expensive for only one plot of farmland. I wanted to know how long one would have to harvest this one plot to recoup the investment. Keep in mind: the following calculation is not how long you'd have to save up for the orb, only how long until the one plot of land has returned the price of the orb, i.e. after how long the orb-investment is profitable.

Assuming that the one plot has a carrot (they are still very efficient) that is fertilised, watered and lit with UV, it will return 35 carrots every 95 minutes. The price for your n-th orb is 10000*2^(n-1). I'm also assuming that the plot is harvested as soon as it is ready. This gives the following: (note: orb is the n-th orb you are buying, cost is its price, harvests is how many times you need to harvest the new plot to have it be profitable, time is how long that would take when always harvesting as soon as possible)

orb  cost      harvests  time
1    10000     286       19d
2    20000     572       38d
3    40000     1142      75d
4    80000     2286      0.4y
5    160000    4571      0.8y
6    320000    9143      1.7y
7    640000    18285     3.3y
[...]
12   20480000  585143    105.7y

Now again, this doesn't mean it takes this long to save up for that orb, only that it takes this long for the orb to "repay" its investment. And yes, you'd have to not miss a single harvest 24/7 for over one year after buying the sixth orb for it to be worth it. And yes, you read that right, the 12th orb repays itself after over 100 real life years of farming in Tsuki's Odyssey.

It's difficult for me to make a judgement on how worth others think this is, and I'd love to have some community feedback on how long you think you'd consider orbs worth it, looking at this. I'm personally leaning towards 5 orbs, because I can get in around 6 harvests a day playing casually and can see myself with this game for the next 2 years (4571 harvests / 6 harvests per day = 762 days = about 2 years). Going much higher doesn't make sense for me personally (even though I now already own more than 5 but my money was faster than my calculations. well...)

I'm interested in your views, because I'm planning on reworking my ideal farming layout with more plot spaces and the new additions from the update and I obviously won't need to plan for 12 orb-spaces when no normal person would ever a) have the money to pay for that and b) see the return on investment in their own lifetime. The highest I'd be willing to look at is 10 orbs (about 26 years until profitable).

TL;DR: An orbs worth depends on how long you plan to play the game after. If you're an active player, sticking with the game for a few more years, 5-6 orbs seem reasonable. If you barely play/are loosing interest, I'd get no more than 2-3. Please leave a comment describing your playing habits (harvests on an avg day and how long you see yourself playing the game) or opinion on this for me to be able to plan for a new ideal farming layout in the future.