I've been tracking "elf production" over the last few days. I ensured that every elf was collected until I got the "no more" message (this involved turning off all buildings, props and ground textures so the eleves hidden behind buildings, and there are a lot of them, are visible).
The current rate is 3 elves / 15 min or 12 elves/hr. Plus there are the additional 4 elves every 4 hrs. So that works out to 52 elves every 4 hours. (Which also happens to be the max cap, since when I left the game alone for more than 12 hours, that is what the max was). This can be as much as 312/d.
So here's the math:
Assume a player is diligent/obsessive compulsive/has no life and hits the cannon as soon as cool down expires and doesn't sleep (so over a 24h period)
- At level 1, they get 6 firings a day, consuming 162 elves with 150 leftover. Total daily bell earning = 324/day
- at level 20, they get 12 firings a day, consuming 540 elves, a deficit of 228; this is impossible so earning caps out at 312*(bells per elf)=2496 Bells/day
At this Rate, the magic level one would assume to halt (where elf consumption exceeds production) is level 13.
But my assumptions are unrealistic so let's make some realistic assumptions.
1) people like 8 hours of sleep
So instead of a 24h window, it is 16. Elf production maxes out at 260 (because when you stop playing, the world will accumulate to the max allotment, so you get 20 hours of production vs 16 hours of consumption)
With this assumption, The magic tipping point actually gets pushed out to level 17.
Now let's look at rate of Returns, not just elf availability.
If you stopped at level 13 (as per the original formula) for every day you do not upgrade, you are losing 312-624 bells (the daily elf max production * bells earned per elf difference). If this is your strategy, you are better off stopping at level 15 instead, The next bell/elf upgrade point) and take your losses.
If you stopped at level 17, you are only losing out at 260 bells/day. By this level, you will only Have a couple days left in the event, so it would be silly to stop upgrading.
Honestly, the math is more complex than I'm presenting and my spreadsheet I've been working with takes more variables into account. I just wanted to make the point that stopping Cannon upgrades is an unwise tactic. In addition, The reduction of elf production is a fallacy; currently they are being produced at a constant rate regardless of level. I toI originally thought that elves were not being produced consistently and were decreasing in rate. It wasn't until I searched until completion that I discovered they are being produced consistently in volume, just that they were hiding from sight due to the environment I created in my city.
So the only tactic I truly would recommend is:
1) turn off the textures Of everything but characters when hunting for elves.
2) grab elves from the cave as soon as possible
3) hunt until completion (notified the town is empty)
4) once town is empty then fire Cannon (once above level 13, there will be times you won't get 3 firings)
5) go to friends towns and only tap on their cannon and/or cave. If either isn't available, skip their town this time around this is significant, as it can earn around 400-600+ bells per day alone. Just following this rule alone for the duration of the event would gain you 10000-12000 bells!)
6) wait for the next cool down period and repeat steps 1-5.
Following this tactic should get all the rewards with 2-3 days to spare.