Is it worthwhile for me to apply for VA benefits after 10 years of separation?

SPC Nate Lamphier I made the decision to file for benefits due to injury over 20 years after occurrence. And was successful. It was a two year process from "intent to file" to completion. It was quite exhausting at times; however, the disability compensation I am now receiving allows me to be financially stable and get reliable medical care. For me it was worth trying.

SPC Nate Lamphier, there is no timeframe on when you can apply for disability compensation from the VA. You can submit a pre-discharge claim when you're within 90-180 days of leaving the service or you can do a post-service claim for your service 50+ years ago (there is no time limit on a post-service claim).

As the time becomes further and further away from your period of service, the two things that will be affected are the complexity in establishing that your illness or injury is service-connected and when the effective date of your claim is.

If you intend to file a claim, the VERY FIRST thing you should do is (assuming you're not going to do it yourself online) is notify the VA of your intent to file* by mail or telephonically. Once notified of your intent to file, you have up to a year to submit the claim, but the 'claim date' is established by your notification.

If you decide to file online yourself (I don't recommend it unless it is something very clear-cut), the date of the claim is set as soon as you start the claim (just opening it .. you don't have to complete it).

You can have a Veteran Service Organization* (VSO) such as the DAV, VFW, etc. (which I highly recommend instead of going down the road by yourself) do it on your behalf, but all it takes is a call to the VA to notify them. When you meet with the VSO representative, mention that you already contacted the VA and gave them a telephonic intent to file and have them verify that "it took".

Looking at your profile, you left the service 11 years ago. What you'll have to show in your claim is that there is a service-connection for the injuries that you have now. That means your medical records (or other types of supporting records) from your time in the service that showed some indication of a 'pre-cursor' condition that was caused by your service which eventually led to what's happening now.

The stronger the evidence included with your claim when it is adjudicated and a decision is made, the more likely it will be decided in your favor.

To put it bluntly - you can't just say "I did a lot of ruck marches", "those ruck marches caused me to have flat feet", and "the flat feet led to my knee and back issues I have today". It has to be documented that A led to B which led to C.

The "B to C" should be easy (a common result of flat feet are knee and back pain). If you don't have medical records showing that you developed flat feet while in the Army, that will be the harder part as flat feet is a common issue that can develop as you age.

A VSO representative will help you through the process as well as advising you on evidence that needs to be gathered.
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* VA Intent to File - https://www.va.gov/resources/your-intent-to-file-a-va-claim/
* Getting help with your claim - https://www.va.gov/disability/get-help-filing-claim/

As the Colonel said, there is no time frame. I didn't apply for my hearing until almost 18 years after my last go round with the Army Reserve. Luckily, I had copies of my last Physical that include an H-3 PUHLUS rating and DA hearing waiver, so that one just sailed through getting rated.
Again, as the Colonel indicated again, it is much easier to get rated if you can document that you had been treated while you were Active. It is a long process to get rated for a presumptive cause without some kind of treatment record.