4/5 developers could (and maybe should be mentors) - assuming they are all competent and all have different skill levels, you could have L5 mentors L4 who ment

4/5 developers could (and maybe should be mentors) - assuming they are all competent and all have different skill levels, you could have L5 mentors L4 who mentors L3 and so on. Related, more cynical take - being a mentor is often a factor in promotion & hiring, and being viewed as a mentor will make you more likely to be promoted or hired.