The study of black holes and cosmic strings in string theory is likely to be a crucial component in the unravelling of fundamental theoretical mysteries (such as the black hole information paradox), while providing a promising geodesic between the defining properties of string theory and experiment (via the possible detection of cosmic string signatures). And yet, the study of such highly excited strings has traditionally relied on effective low energy descriptions, which break down in the UV and at small scales, and where the characteristic infinite tower of oscillator states and inherently quantum-mechanical processes (such as string intercommutations) are not captured. To understand the significance of the physics one is neglecting (which is likely to be large as indicated by the information paradox for example) one would like to go beyond an effective description. par Working in the context of the full perturbative string theory, in this talk I will present a new and (as I will demonstrate by an explicit decay rate computation) very efficient approach to interacting highly excited strings which transcends the aforementioned shortcomings of effective descriptions, based on a covariant coherent vertex operator construction. I will go on to present a new perturbative duality associated to all excited strings, discuss the limit where a low effective description emerges and discuss new alpha' corrections to decay rates of highly excited strings.