There are a lot of assumptions in this statement worth examining:
1. A productivity system must work for a long time.
2. A conversation about productivity systems must exclude those that are in the "doesn't work" and "interesting new idea" stages.
3. Productivity systems and workflows are not personality (or personality type) dependent - what works for one person doesn't qualify as something worth investigating by those who identify with the "successful user".
I think #2 and #3 stand alone, but #1 is a bit more interesting:
There exist people for whom any productivity system will not work in the long run. There are several factors that can be involved in this:
* they are actually more productive when ramping up a system and early in using it - the thinking about the system to productivity inspires actual productivity. Once they internalize the rules and the ramp up, it stops working because they don't focus any more
* The sort of person who internally chafes at rules/structure may experience productivity at first with a new system, because (s)he as decided to comply with that system, but subconsciously starts to figure out ways to meet the rules of the productivity system without actually being productive. Some people just do this, whether they intend to or or not, it's just a thing.
* Novelty itself inspires them to do more
* Productivity inspires productivity - the act of setting up a productivity system is productive, therefor inspiring other productivity elsewhere. (similar to the first example but a bit different)
And so on.
Why not give such people another system or lifehack or workflow hack or whatever you label it, to chew on?
(ok I claimed I'd leave #3 alone, but experiments like this allow people see more things that work for someone a bit, and help give them ideas to tailor the system to themselves)