This paper studies reduction congruence \cite{short:HondaK:redbps} for the asynchronous $\pi$-calculus with timers \cite{short:MartinB:twophacpiaepc} and derives several alternative characterisations, one of them being a labelled asynchronous bisimilarity. These results are generalised to an asynchronous $\pi$-calculus with timers, locations and message failure. In addition we investigate the problem of how to distribute value-passing processes in a semantics-preserving way.