You need to decide if you want 3 pieces of AE or 4 pieces of AE. It cost 300 tokens to fully upgrade each piece of AE. This does not include the tokens it cost to build it or shop for it or buy it or move it to another piece and so on.
When your players hits day 280 he no longer gets training points or bonus tokens. So you need to do the math and figure out how many tokens you will need to reach your goals.
Usually around day 150 you should sit down and calculate things out. Switch to light training for the 6 tokens a day once you know when you need to switch to reach your goal.
Originally posted by Hagalaz as a general rule, day 160 if 4 pieces of AEQ, day 200 if 3 pieces if you don't spend too many BTs
Exactly. That's why I said around day 150 you sit down and figure it out. You may not be able to get 4 pieces of AE if you didn't work your tokens right and that would allow you to multi train longer and still get 3 pieces of AE.