Nescis quid ha’beas, a’ntequam interi’erit
1. I don't know what those apostrophes are supposed to signify.
2. Nescis quid habeas is what is called an "indirect question". One uses an interrogative (here quid) and the subjunctive (here habeas). "You don't know (what you've got)". In my opinion it is OK here.
Non aestimas quae habes instead uses a relative "You don't value (those things that you have)". In my opinion this is also correct. This could also be put into the form of an indirect question: Non aestimas quid habeas..., which in my opinion combines nice features of both of the others.
3. Antequam and quoad are both ways of saying "before" or "until".
4. Interierit is ambiguous. It could possibly be the pefect subjunctive active third person singular of intereo, but is probably intended to be the future perfect indicative third person singular of that same verb (the subjunctive after antequam has special connotations). Interierit is, I think, a reasonable way to express the idea of the thing insufficiently valued "going away" or being lost.
Discessere is a poetic alternative for discesserunt, the perfect active third person plural of discedo, another perfectly reasonable verb to denote the "going away". In fact I like discedo here better than intereo-- but that's just a matter of taste, I think. The tenses are tricky. I have to admit that the future perfect of whoever authored the intereo version is better (or at least "more Roman") than the perfect of the discedo version. The Romans tended to be more logical than Anglophones in this regard, and would very likely have used the future perfect: "until it shall have gone away" rather than the perfect-- I think the perfect is defensible, but I agree that the future perfect is better.
5. Once again, we might combine the better features of each version (or at least what I feel to be the better features of each version):
Non aestimas quid habeas quoad discesserit
6. In summary, the version atop this post is (if we ignore the mysterious apostrophes) another way of saying the same thing. It has features that I prefer (the indirect question, and the future perfect for the last verb) and features that I do not prefer (nescio for non aestimo, antequam for quoad, and intereo for discedo).
You might show my "compromise" version to the author of the Nescio version, and see what he thinks.
Hope this helps.