Re-pressurizing balls will only work up to a limit.
After trying the Tennis Ball Savers and re-pressurizing them to above 14 PSI by using the freezer method, in addition to the using the pressure less Triniti and Triniti Pro I've made the following observations:
1. Despite being re-pressurized, used tennis balls lose their bounce rather quickly. All new balls, especially the Penn Champs have a brief 15 minute of extra liveliness fresh out of a can, which drops off in a similar manner as balls that have been re-pressurized, but at a faster rate.
2. Triniti has a good consistent but low bounce, and is challenging to play consistently compared with other fresh tennis balls. Broken in, but not overly used Triniti tend to have a more flat trajectory, and also tend to land more short coming off the racquet. Nonetheless they remain superior over 'zombie', aka very old pressurized balls and re-pressurized balls in terms of bounce.
3. Triniti Pro, from their marketing, has the same rubber core, but is instead made with a 'Pro' version of their long lasting Felt. However upon holding in the hand, it appears to be somewhat softer to squeeze and plays well sooner out of the paper can. Triniti Pro has a more loopy trajectory than the Triniti, and flies longer than Trinti, closer in performance to a fresh can of balls.
My guess for point 1 is that the rubber contributes significantly to the bounce of a fresh can of pressurized balls, and re-pressurizing older balls won't replicate new balls well enough.
My guess after point 1 and 2 is the special felt on the pro allows a bit easier break in as well as better playability when compared to a fresh, since a tennis ball is composed only of two components - the rubber core and the felt.
-The felt is very important changing ball trajectory when hitting with spin, as confirmed with experiments by TT university. I have also observed in person and in combination on reading the forums about Triniti's relatively poor play on clay courts. Now just reading about the ball machines and how they have varying effects on tennis balls, it seems to matter how much spin is being imparted.
Just my two cents