For projects where I have a paying customer, this rule is absolute; I do not experiment on my client's time (and dime) unless they specifically request it. But

For projects where I have a paying customer, this rule is absolute; I do not experiment on my client's time (and dime) unless they specifically request it. But I do have projects which I finance myself (with myself as customer), and which do not have a real deadline. I can experiment on those. Call them "hobby" projects if you insist. > Applied consistently, this logic would seem to preclude becoming familiar with anything. Well, project requirements always rank higher, and many projects require some piece I am unfamiliar with (a new DB - e.g. MSSQL; a new programming language; etc). That means one does get familiar on a need basis , even applying this approach robotically. If a project requires building the whole thing around a new shiny technology with few users and no successful examples I can intimately learn from ... I usually decline taking it.