Does the obligation to enjoin good and forbid evil remain in effect if it is postponed for a period of time, whether long or short, for reasons such as verification, preparing advice, or being preoccupied with life matters?

Enjoining good and forbidding evil is an immediate obligation, and it is not permissible to delay it unless there is an overriding benefit. If you delay forbidding evil for a benefit, then you must immediately enjoin it once that benefit is realized, unless you know that the perpetrator of the evil has repented from it. An example of this is a woman who displays herself immodestly (mutabarrija), whose advice was delayed for a benefit. Once that benefit is realized, it becomes obligatory to advise her, unless she has repented and veiled herself.