About 90% of the stellar build-up in galaxies occurs gradually on the main sequence, with the tightness of this relation (at the level of ~ 0.3 dex) being commonly interpreted as a consequence of the self-regulative nature of galaxies. However, within this framework, it is currently still unclear whether there are multiple pathways of stellar mass growth. In other words, does the observed scatter stem from systematic long-term differences in the star formation histories of galaxies that differ in their sSFR today (set e.g. by variations in halo assembly)? Or can the spread simply be attributed to short-term stochastic fluctuations in the growth rates of galaxies (traced back to e.g. variations in gas inflow, minor mergers, "breathing" cycles consisting of star-bursting episodes followed by a suppression due to feedback)? In addition to defining the timescales on which the main processes regulating star formation operate, these scenarios are also indirectly related to the end of the lifecycle of galaxies. By discriminating between a predominantly smooth or bursty evolution of galaxies, quenching may be interpreted as a natural progression of continuously declining star formations histories (slow quenching) or a disruptive process (fast quenching). I will present new insights into the the star formation histories of massive star-forming SDSS-IV MaNGA galaxies, as reconstructed via full spectro-photometric fitting with the novel stellar population synthesis code Bagpipes (Carnall et al., 2018).