maybe it takes 10 years to adequately break in a good speaker.....?

So maybe a better question would be based on the fact that the event 20/20s 1st gen were produced in the early 2000s would I see a significant Improvement by purchasing newer monitors? And if so, what would you recommend that would be close to the $500 price range and similar to the event 20/20s? Thanks

You'd probably have to go up a notch in price to get a significant improvement. Even if money isn't a barrier, there are two other considerations:
1. Investing in acoustical treatments will give you a bigger payoff than new speakers, assuming you don't already have plenty of bass traps and absorption. This is especially true if your new speakers offer better low-frequency response.
2. New speakers will require you to re-train your ears. You've likely been listening to those Events for so long that you subconsciously know what a good mix is supposed to sound like on them. Even with better speakers, you'll need a break-in period (not for the speakers, for your ears).

I've had a pair of Mackie HR824s for the better part of 20 years. 

My NSM 10's are now 20 years old and seem to be as they where when new.
My first monitors were my Tannoy PBM 6.5. I blew the HF drivers ( accidents do happen)  and replaced them with drivers from my Yorkville parts catalog as I was a dealer at that time.  I think they were an improvement.  Later the LF driver foam fell apart and I found some "Made in Canada " replacements that were identical in all ways to the originals and only $30 each. So they are still driving my office/ TV /Hi Fi set up and those I bough 30 years ago.

I've got a pair of locally (Australian) made Transound Systems 2 way passive speakers with Kef drivers that I bought new in 1987.
About 30 years by my reckoning and they still have real clean highs with tight punchy lows. I'm currently driving them with a Marantz SR96 THX 5.1 surround Reciever. I use for home listening and comparison if needed.

BobF
My Event PS8s have been with me since '00 or '01 or there about.

+1. I've had my Precision 8s for about 10 years now and they still sound great!!! I have been looking around lately for an "alternate" set of monitors, mainly for reference.

I have pair of Event 20/20s that have been used for myTV speakers for around 20 years.
I thought they sucked in the studio.

If it helps, I use:

(2001) Mackie HR824 ver. 1 (2001 models)
(1989) Polk Audio SRS-SDA 2.3tls, powered by a Pass Labs X350
(1985) Radio Shack Modulaire 800 (boom box)

All of them are in great shape still.

Studios still use Yamaha NS-10's, and some are the really old, nasty sounding ones you need tissue paper for.

Microphones fall into that sort of discussion, too. :)

I've been mixing on the same pair of 6.5" Tanoy's for 25 years.