I think we all have to fine tune in our own way--
Some actions that are context specific can be done across projects in a bunch--so the next actions listed by context works great then.
This is especially true for people's lives that are so spread out in regard to context, for example, I work in an office that has no internet, so anything I need internet for that is work related I must do from home. I live far from any good produce markets so if I set off in the direction of one I want to get any fresh fruit or veggie I anticipate using in three or four days' time.
But as noted by the initial poster, some projects are better worked on in larger pieces. In fact, if I am going to write, research, sort out stuff, I need block of time and to be in the right context(s), such as @home, @library. I think that maybe if we are trying to plan the work ahead maybe for these types of work it might be helpful to identify times on the calendar that accomodate these "intensives" and maybe on the next action list put the action but also indicate that it will be the entry point into something bigger and/or some time guestimate (e.g. "@ phone get attorney's feedback" is something different from ""@phone confirm dentist appointment). Similarly, "@errands-return sweatshirt for a refund" is different from "@errands-try on frames for new glasses (1 Hour )" from "@errands-take all three children for athletic shoes (2 hours)".
I am also thinking that if the deeper more intensive work is part of one's regular work, maybe the "best" practice is to have regular times for it in the day or week or month or whatever fits you.
I would love to hear how people handle this type of thing who do it effectively.