Zef's reply seems to be right on. I'm at about 250 dives in a Fusion Tech with the old Dry core, and the only leaks it's ever had were around the ankle join where my Evo3 boots rub. I dive BP/W, so after 250 dives, there's a slight wear point at the bottom of the plate, and a little discoloration from the crotch strap. I also dive doubles and sidemount, and have never noticed any issue with tech dives other than the lousy Fusion Tech pockets. It's probably due a new skin, and overall, when it's time to replace, I'd probably look at a new Bullet. The Aircore is supposedly easier to pull on, the ankle zippers allow easier entry of feet, much better pockets, and the outer skin is more flexible than the previous Bullet (I'm told).
I had about 3 weeks of diving an older Fusion Sport DryCore suit before I got my Fit with AirCore.
AirCore is much easier to pull on. It's also easier to get off! My Fourth Element Arctic socks would stay in the DryCore when I tried to take it off. They stay on my feet when I take off the Fit with AirCore liner. The ankle zippers really help, too!