Regarding the natal plum, the first year mine flowered a lot with no fruits. This year, however, it has flowered and fruited seemingly non-stop. It has about 5-10 fruits on it at any given time. So you should get rewarded next year if that is their pattern.
Also, their flavor is not out of this world, but it does grow on you. And the latex issue doesn't help either.
I'd be happy if at least 2-3 of my trees started fruiting for the first time every year. That would definitely be worth it.
The frustrating part for me is when a tree flowers without fruiting. It's happened on my Ross Sapote and especially on my Ice Cream Bean. It is constantly flowering but never sets fruit. It is over 30 ft. tall with plenty of flowers. It must be related to pollination.
Another frustrating plant is dragon fruit. I gets loads of flowers, but very little fruit, even though I try to be diligent with my hand pollination, but it may need a different variety. Here is a pic of the plants about to bust out flowering on top of my shed:

Jaime