  Real scalar fields with attractive self-interaction may form self-bound
states, called oscillons. These dense objects are ubiquitous in leading
theories of dark matter and inflation; of particular interest are long-lived
oscillons which survive past $14$ Gyr, offering dramatic astrophysical
signatures into the present day. We introduce a new formalism for computing the
properties of oscillons with improved accuracy, which we apply to study the
internal structure of oscillons and to identify the physical mechanisms
responsible for oscillon longevity. In particular, we show how imposing
realistic boundary conditions naturally selects a near-minimally radiating
solution, and how oscillon longevity arises from its geometry. Further, we
introduce a natural vocabulary for the issue of oscillon stability, which we
use to predict new features in oscillon evolution. This framework allows for
new efficient algorithms, which we use to address questions of whether and to
what extent long-lived oscillons are fine-tuned. Finally, we construct a family
of potentials supporting ultra-long-lived oscillons, with lifetimes in excess
of $10^{17}$ years.
