Which rubber are you thinking to buy?
Most "factory tuned" rubbers don't really need to be re-tuned. They mostly just keep their out of package playing properties.
Now obviously I don't understand what tuning means. My understanding was that factory tuning means factory boosting of the sponge and this is why these rubbers come in a sealed package unlike most regular untuned rubbers. The boosters cannot last forever because if liquid, they must evaporate somehow & the sponge becomes essentially dead or less springy or whatever ?
That still does not address my question as to whether (factory) tuning is same as boosting. Just a question , not blaming you.Well factory tuned rubber is probably sitting in the warehouse for some weeks or months before it is sold and reaches the customer. So what I have found is that factory tuned rubber is a little bouncier out of package compared to non-tuned rubber, but generally does not lose its bounciness over time.
For example, I have a sheet of Yinhe Big Dipper which I bought in 2017. Even today, its still just as fast and bouncy as a brand new sheet of Big Dipper which I bought in 2022. In fact, I think the 2017 batch was a little better and even faster.