than (on) their intensity

[keannu]

The original text has "on" in-between, but is it a must? It's connected to "depend" and this is a grammar question, but I don't know if this kind of rule is quite strict.

ex)Making $1 million in one year, but nothing in the preceding nine, ①does not bring the same pleasure as having the total evenly distributed over the same period, that is, $100,000 every year for ten years in a row. The same ②applies to the inverse order ― making a bundle the first year, then nothing for the remaining period. Somehow, your pleasure system ③will be saturated rather quickly. As a matter of fact, your happiness depends far more on the number of instances of positive feelings, what psychologists call “positive affect,” ④than (on) their intensity. In other words, good news is good news first; how good matters rather little. So to have a pleasant life you should spread these small affects across time as⑤evenly as possible. Plenty of mildly good news is preferable to one single lump of great news.

[SoothingDave]

It's optional, but with that many words between I would include it.