How to tell if Eames 670 lounge shock mounts are going to break?  

No warning it will be pa...
No warning it will be painless and deadly something that you can not prepare for, you will know it when it happens as the shock gives way and on one side it will be, the other just a a impression of the shock mount,
But don't worry go about your normal life ,drink your brandy and have fun, and you can get it fixed like the rest of us have.

Thanks for the reply. I...
Thanks for the reply. I checked with the original owner of the chair and it has never repaired. My next question:
Should I just have the shock mounts replaced as a precautionary measurement or should I just wait for the inevitable?
fm

I would just wait for the ...
I would just wait for the day of destruction You might be the lucky ones that it might never break but when it does you will be prepared and know were to go.

I was holding my breath
when my 300 pound brother plunked himself down on my prized Eames 670 lounge yesterday.I couldn't say a word,because after all,he had stopped in to fix my computer.He was so impressed with it,he might buy one for himself.As he rose to get out of the chair,I(felt bad,but) asked him not to push down on the armrests as he got up.Anyhow,the 'ole Eames took it like a champ;not one groan of protest nor a creak,and thank goodness,not a crack!

i feel and know your pain ...
i feel and know your pain I bought a chair on ebay and did a major redo from shock mounts to re finisher and redid the leather my wifes first sitting after knitting she pulled up and
pulled off..... back to the re finisher with this one I hate to say it but now we just look at the Icon we really never sit in it
I know people will say what good is it ?????? but I really never sit on my Caulders Vaserally, or original Andy Warhols
I like to keep this chair Iconic and pristine and just shy the people nicely away from sitting a spell in the old EAMES Chair

one thing you might think ...
one thing you might think about take a Knife or sharp blade and a magnifying
glass take the knife and lighty scrape the shock mount if it flakes you will know that it will not be long now...... before it needs to repaired .... If it hard and you can see glue around the original shock mount you still have some time . the harder the worst that they are .... but nothing will happen until it wants to give way . the shocks should be somewhat hard and rubbery, It is the glue that gives after 50 years, The only thing that i hate to scare you about is when heavy people or any one for that matter pulls up and tries to get out of the chair that is how it pulls and a lot of blunt force will pull the first layer of plywood and that is wear the real problem and expenses comes in So if you can shy people away from the old gal you might be better off,

Scared!
This is sounding like a scary movie, I'm almost afraid to sit in my chair now! I also weight in at about 220lb, but i'm real gentle with it and it's only sat in by me. I just got it last year(50th anniversary), so i'm probably ok. This thread will be in the back of my mind for the rest of my chair life.

You needn't worry about the5oth Anniversary
model.This is factory fresh and has half century of use before you need to worry about shockmounts.Don't fret-Enjoy!

you have a lot of miles b...
you have a lot of miles before you need to replace those shock mounts they were made in in the 21 century with the finest products, your good for a long time

that's a good point
I wonder if today's lounge chairs employ a different glue? I wonder if they will hold up better in the long run.
My girlfriend and I sometimes both sit in it and together we probably weigh just short of 300 lbs. Should I not do this? Although these stories concern me a little, mine is only about 5 years old ... but still.

I would not do that .... ...
I would not do that .... I think it is sweet you and the little lady like to be so close... but for some reason my chair made in the 70's scares me, Like i said I had it completely restored from head to toe and on its maiden voyage my wife pulled up on the arm (not her fault) we found out from Alfi Hume that the epoxy really needs to bond and cure out for at least a 10 days, before you set in it . I know the construction of today is far superior then 30 years ago on those chairs , but for some reason just knowing how they are made with the shock mounts from inside I would not put to much wait on the chair.

LRF,
Thanks for your...
LRF,
Thanks for your thorough replies. The previous owner and his wife are both of fairly small builds (150 lbs max for him, maybe 100 for her). My wife and I are similar builds. We'll refrain from bearing down on the arms when we get up and take our chances.
fm