Aircon Regas as a preventative measure?

[Riknos]

I’ve got 2 cars with perfectly working aircon but they haven’t been regassed in the 5 + years I’ve had them. I understand a sealed system shouldn’t leak but would it be worth it just to get Fresh oil on the seals to make them last longer? One car is 18 years old the other 14, for £35 a pop is it worth it as preventative maintainence?