Took my 535 in last week for a new pickup to be installed in the bridge position. The Railhammer Hyper Vintage was a nice sounding pickup, but really bright. I found myself constantly adjusting the tone controls. I've come to realize that pickup design works best for people who tune down a lot and use lots of gain. Not exactly the type of pickup commonly found in a semi-hollow body design. So I had a custom-made Red Rock Alnico III humbucker made for the H535.
Since this is a semi-hollow body, I don't trust myself to install it. Instead I paid for an old tech of mine to do the work, to me, its worth the price paid.
However, the point of this thread is not about Red Rock pickups but more about the old tech I used.
This gentlemen ran a very popular music store in Royal Oak for a couple decades that provided guitar tech services, gear rentals, and even lessons in guitar, bass, and drums. (Fun fact, his drum instructor at the store was Chad Smith right up until he was recruited to join the Red Hot Chili Peppers).
In those years, he has seen hundreds of Heritages guitars come through that front door. While he sold the business/building years ago, he continues to work out of his shop in his basement.
He is rather amused how much I like Heritage. He kinda of shakes his head about it but ended up telling me he's seen a lot of bad ones come through his door. Recently had a 575 come through that had some weird pickups that were solid black (a lot like an EMG). What was not noticeable until he did a pickup swap with a normal pickup with pole pieces, did he notice the bridge pickup was so poorly misaligned. He said there was about a 1/4" offset to the pickup. He's never seen one that bad but mentioned how many of the Heritages he's serviced have terrible quality controls.
I agreed with him to an extent. We all love our Heritages, but until they went under new management and manufacturing standards did Heritage's quality control improve. Heritage had its charms of being unique, custom, hand-made instruments from 1985 to 2015. However the uncontrolled environment and build methods would sometimes lead to a varying degree of quality. Just like Fender and Gibson in the 70's, Heritage also suffered from loose quality standards for many years. There are a lot of gems out there but also there are some dogs...
So when people ask for the best years, its all subjective. For unique finishes, appointments, and typically slim, fast necks, go for the older stuff. For a consistent quality, choose newer stuff. Just my $.02.