Regarding the cost (in time) of spending time:
My take on the challenge here is that you're modeling a method of assigning value based on the causal relationship between performing an action and the direct impact of that action on the desired goal. I'll reference the above elements as processes of 1) assigning value to individual actions based on causal relationships, and 2) determining a causal relationship between performing an action and its direct impact on the world.
In this model, an efficient action is one where we can clearly determine that its rationally causal relationship with impact on the world contributes to our desired goal. More importantly, in this model it is important that the action contributes to our desired goal directly.
Consider an action that is homeostatic in nature - spending time buying food does not directly contribute to our desired goal of "engaging in the act of kayaking"; as such, it isn't valued as efficient in the above model.
We do recognize however, that buying food is a irreplaceable step in the system of actions required to "engage in the act of kayaking." To the extent that an individual action is irreplaceable in a system of actions required to accomplish a goal, that action is important and valuable [this is a premise I'll call the irreplaceability premise]. With this premise in mind, it is easier to see that the act of buying food has an impact on "engaging in the act of kayaking" that is just as important as the act of pushing the kayak into the water.
Using the directness model, we consider buying food as less valuable because it is less directly related to the happiness we experience from kayaking. If the irreplaceability premise is well-founded, then the directness model is a weak method of assigning value to actions - and thinking about irreplaceability may help resolve some of the concerns that later arise with how to most optimally spend one's time.
[As an aside, it's important to note that this application of the irreplaceability premise is founded on the notion that if the act of eating is removed, the act of pushing the kayak into the water will never take place. We can easily imagine an alternative scenario - you push the kayak into the water while hungry - so I'm supporting this irreplaceability with the sentiment contained within the statement "my desire to go kayaking is not strong enough to override my desire for food." It is in fact worth considering the function of time and our ability to delay homeostatic actions in this notion of "irreplaceability," but as an absolute definition, homeostatic actions will always be necessary and ultimately irreplaceable - it is equally easy to imagine an alternative, lengthier goal where delaying homeostatic behaviors ultimately do not reduce their necessity.]
To help make the irreplaceability premise more clear, consider also actions that are not homeostatic. As an undergraduate, I would often be conflicted about the directness of my actions and how to assess their value - most notably when the desired goal was something like "delivering a presentation for a class final." At some point it occurs to you that you're spending hours or even days preparing for a goal defined as a 20 minute task, and this seems like the same kind of waste mentioned above in the expression "it might take me 4-7 hours to get ready to kayak for 1-2 hours." But it is relatively easy for one to intuitively see a causal relationship between preparing slides and organizing sources as important to the end goal, so operating under the directness model our worries of wasted time are at least somewhat assuaged.
The problem is that the directness model again breaks down over lengths of time, where irreplaceable actions are not intuitively direct actors in the causal relationship between action and goal. 30 seconds of the presentation may come from ideas fostered over hours and hours of time going to class - and worse yet for directness, they may reflect the synthesis of disparate ideas captured across various chunks of time spent in lecture.
I'm not necessarily sure that the irreplaceability model is any better a tool for assigning value in our attempts to calculate efficiency (in a complex enough system it quickly becomes easy to identify every action as irreplaceable), but the above examples help illustrate the challenges of assigning value based on direct causality.
Hey friends. I was able to join in a couple of fascinating LW/OB NYC meetup conversations; I don't comment here much but certainly read daily. Thanks for all the thoughts/insight.