I had no problem detecting the coconut in my beer months after brewing using less than a pound. It really depends on how much coconut flavor and aroma you are going for. I have no trouble believing that SOME of the coconut is going to fade over time, in the same way that dry hops will fade over time just because the beer gets older. Taste a fresh IPA a week after dry hopping and the same beer again at a month, and it will have much less hop punch than it did a few weeks before.
Maybe start with a pound, see how you like it at that level and keep some bottles around for a few months to try at different stages. Then, use that to determine what you do on the next batch. Personally, I use 10-12oz as I wrote in the recipe. I like being able to clearly taste the underlying style without the beer being overwhelmed by the fruit. A lot of people like their fruit beer to be dominated by the fruit, but that's not really my thing. There is a lot to be said for balance.