The distinction between "accent" and "pronunciation" instruction is important in the field today. It is essentially this: The goal of pronunciation instruction should be intelligible speech; the speaker is understandable without unduly taxing the ear of the listener. Accent reduction, on the other hand, appears to go beyond this "intelligibility threshold" aiming at more and more native-like pronunciation. There may be any number of reasons to "go near there," of course, including working at an international call center, managerial or executive positions where public speaking persona may still require a certain degree of conformity, such as consular representatives--or, of course, secret agent types!
So, how fast can a learner's accent or pronunciation change and get to a goal or model?
Purely anecdotal evidence from about 40 years of working with accent, suggests that for most students it is a relatively long and incremental process--if attempted at all. There are those of amazing natural ability who almost chameleon-like appear to absorb the second language in all its multifaceted dimensions, accent being just part of the picture, of course. In truth, however, most of those who approach a native-like accent work at it, often for years--or longer. If it is worth doing, for only some, mind you, how do you get there?
One way, of course, could be to go to SpeakMoreClearly and help them become more affluent in getting you there quickly. Or . . . you might, however, want to consider this new research by Hampton, Asadi and Olson at Temple University, Good Things for Those Who Wait: Predictive Modeling Highlights Importance of Delay Discounting for Income Attainment." (Summarized by ScienceDaily.com.)
What their research demonstrated was some validation of the old saw, Good things come to those that wait! In essence, children who were trained to postpone the natural drive for more instant gratification (had more self control), later in life made significantly more money. From the ScienceDaily summary:
"Unsurprisingly, the models indicated that occupation and education were the best predictors of high income, followed by location (as determined by zip code) and gender -- with males earning more than females. Delay discounting was the next most-important factor, being more predictive than age, race, ethnicity or height."
So how does that work for predicting success at obtaining great pronunciation or accent?
(occupation and education) -- (zip code and gender) -- delay discounting. i.e., self control/delayed gratification -- (age, race, ethnicity or height)
That actually might work, as long as you flip the gender (from male in the affluence study to female!) and begin the study at age 12 or so. That would be particularly the case if you factor in DD.
When it comes to training the body in the gym, the DD principle is a given. Self control and persistence is the only way to get to excellence--and stay there. And what that entails is adopting a commitment to the process, over time, not some abstract goal in the future. In most respects, quick fixes are only temporary, at best. For a great perspective on that, check with my favorite source on such topics, James Clear, here or here!
So, what is your best plan to achieve "a fluent" accent or pronunciation?
DD-based practice over time (done as embodied and
haptically as possible, of course!) . . . and you can take that to the bank!