Depending on the agency and the worker and the field, it usually takes “about” a year for a worker to pass from initial expression of interest through application, vetting, fundraising, and on to the field. (More pre-field training requirements—like college or seminary—will of course stretch this time.) Once on the field, it can take a year or two (or more) to become proficient in the language and culture.
Once a movement strategy is being pioneered, it can take several years to reach 4th generation in multiple streams (sometimes far longer—note theological assumption Only God starts movements).
Therefore, all attempts to initiate a movement amongst a new people group or segment should be predicated on a minimum 5-year investment before any fruit is expected, and likely 10 years before fruit/harvests are “very large” (such as 10 to 100 thousand believers).
Anything “shorter” is very probably not going to be sustainable transitioned into something “longer”: in other words, you can see fruit in a shorter time (from a short-term trip, or a quick church planting), but these strategies aren’t multipliable, don’t see the extended ramp-up that defines an exponential curve, and so won’t be long-term sustainable or reach very large numbers.