In business management the Pareto principle, or the law of the vital few, translates into the notion that 20% of the clients bring in 80% of the sales. I argue that in science the same principle applies. Here, focussing 20% of your time on necessary projects will translate in the bulk of your output.
I often use this principle, limiting the amount of time allocated to critical tasks to 20% of my time (mostly through automation). The remaining time I use to keep other projects running including a fair number which have the potential to turn into high output (20%) ones. The latter is important to keep a steady stream of fresh ideas (and potential funding going).
To keep my sanity, and an overview of running projects, I use a Kanban system, centered around the notion that everything is an (R) project. Kanban is a scheduling system originally used in just in time production, but can be applied to any task at hand. It is especially suited for project development.
In this system you visualize tasks at hand on a Kanban board (see below) which makes tracking progress, or backlogs easier. As such you can balance your capacity across multiple projects.
I maintain three folders storing (1) working projects, (2) those on hold and (3) the ones that are in review or accepted. Projects in the review or accepted folder require urgent but little attention in term of time. Working projects are those where the bulk of my attention goes, while those on hold represent potential. Projects on hold can either be rejected or evolve into working projects if they show potential.
Balancing the Pareto principle in a Kanban system (squeeze) allows me to maintain efficiency, and a variety of projects moving forward in the bussiest of times.