What's so special about '50'?

[Hilde Bracegirdle]

And 40 is often regarded as the beginning of "middle age". Or we could figure things in terms of the death date. If the average hobbit dies at 92, then 50 is more than half-way there, making it again equivalent to about 40 years in human terms.

Ah! It makes me want to run out and paint my door green, maybe put up a few extra pegs by the door incase some dwarves drop by!

A great doom awaits you, either to rise above the height of all your fathers since the days of Elendil, or to fall into darkness with all that is left of your kin. Many years of trial lie before you. You shall neither have wife, nor bind any woman to you in troth, until your time comes and you are found worthy of it. - Elrond to Aragorn - RoTK Appendix A

It came to pass that when Aragorn was nine and forty years of age he returned from the perils on the dark confines of Mordor, were Sauron now dwelted again and was busy with evil. - RoTK Appendix A

At this same age (49) Aragorn betroths himself to Arwen at Cerin Amroth.

Basically, I bring this up for quite a few reasons, one being to point out that the importance of fifty-ish is not exclusive to hobbits.

Initially, I didn’t think much about the fact that Aragorn was so near 50 when he “plighted his troth”, but when one reads Elrond’s speech the significance seems much greater. Aragorn’s time had come and he was found worthy. (Of course he had hung around Gandalf quite a bit by than, so maybe the Istari’s notion of an appropriate age had rubbed off on him as well!)

I also find it curious that Tolkien specifically mentions ages, although he had previously said this took place nearly 30 years after meeting Arwen at age 20. It is as though he wanted to make sure we knew just how old the character was when this happened, and not just leave us to do the math on our own. So I do suspect that there is something significant about fifty(ish) in his eyes.

Can anybody find anymore references to 50 hidden somewhere?