I have no doubts that you will have better longevity using this seal kit over others.
I gutted my 1984 cremina, and saw horrible scaling on the piston and inside the tank, plus was experiencing rough shot pulling and leakage from the piston. This kit solved most of those issues.
However, there is a difference between the red portafilter gasket and white group gasket included and the more durable black ones that comes stock with the machine. I do not think that they sell those anymore, and the red/white seals do fit just fine.
After changing the piston seals, I noticed that the old seals were pretty loose in the piston. The new ones flared out a bit more and are nice and snug. The portafilter gasket required some work to get in place, but after many times installing / removing the portafilter itself, it appears to have settled and fits properly.
Please buy Dow 111 and citric acid (descaler) with this kit. Lubrication and descaling are 100x more likely to help you than replacing seals, since I still have the same leakage after installing this kit. I do however, have a much stronger and smoother shot after cleaning.