Just wondering if there's any way to stop losing the tremolo arm spring (every time you screw the arm in and out), and basically if it's essential to have it in there in the first place ... any answers?

I have been wondering the same today... Odd enough, there has been no improvement over the last 50 years... The spring is essential for the arm to stay where you want it to. I have thought of sticking a small piece of masking tape over the hole of the tremolo arm, but I know this is not really easy to remember and I am going to lose it sooner ir later.

Any ideas anyone?

Buy a dozen and keep them in your gig bag

Cut a piece of (electrical) tape round (a little bigger than the hole diameter) and put it on top of the spring inside the hole - this should keep the spring from falling out.
Or rely on an old Fender-originated (?) advice: put a dab of vaseline in the bottom of the hole to keep the spring in place.

Anyway, those springs are sold in bags of twelve, so when you order you will have plenty for replacing the first replaced spring.

That spring is there to give the trem arm some resistance so it won't wobble freely - although apparently Hendrix didn't use the spring (maybe he, too, lost it...).
No spring may result in trouble finding the right tension for the trem arm, thus ruining the threads (& goin' blind & growing hair on your hands etc.).

Mind as well forget about that spring and learn to do without, it will always find it's way out.

In the past I have used teflon tape around the trem arm to help it tighten up and stay in place. This way I could get away without hearing dings and dongs from the arm play in the hole. But, teflon tape wears away once you unscrew the trem arm to put your axe in the hard case. So there are a few options I guess (for all of us here with vintage trems)...

1. Teflon tape
or
2. Dozen springs
or
3. vazeline at the bottom of the hole to keep the trem spring in place (it would reduce friction too I suppose
4. Any other ideas?

Depending on which hard-case you have you may be able to just leave the arm attached. I leave the arm always attached to my 62HR and when placing it in the vintage style case, I point the arm tip in the direction of the output jack, when closing the lid there is no interferance. Of course check the situation with your own guitar/case, but mine is fine with this technique and I prefer it to screwing/unscrewing the arm all every time, which may end up causing other issues anyway.

Snowy