I completely agree, and thank you for raising this issue. An inactive party shouldn't be able to reactivate and immediately dominate its nation by using its stored-up high visibilities from the distant past.
This doesn't even make intuitive sense. Let's say a party had been prominent in some nation a century ago, but for some reason it abruptly disbanded at the height of its popularity. Time passes. A century later, some citizens decide to get together and form a party under the same name as that one from the past (the equivalent of a party reactivating). Why should that new/revived party somehow immediately be declared the most prominent party in the nation, merely because its ancient predecessor had been the top dog back in our great-grandparents' day?
The simplest way to solve this problem would be for, if a party goes inactive, its visibilities to get set to zero at that time, as part of the deactivation process. If it later reactivates, it has to start again from scratch.
Unfortunately, this would have the unpleasant side-effect of, if a player accidentally deactivates, or gets deactivated in error, all of that player's party's visibilities will have been wiped out and need to be laboriously rebuilt again from zero.
I recommend a middle course.
Active parties gradually lose visibility as months and years pass. Let's simply apply this same process to inactive parties as well, treating them the same as active parties are treated for decay of visibility over time.
Of course, active parties can vote on bills to fight this trend and increase their visibilities. Inactive parties can't, so their visibilities would just slowly drift down until they hit zero ... or until they reactivate and start voting again.
Better yet, I feel that this would also be the most realistic way to handle this situation.
A real-world party that revives after a year or two of dormancy, will still have a lot of people remembering it and being willing to support it, although fewer than if the party had been continually active in the meantime. By contrast, a real-world party that collapsed a century ago, would be remembered by only a handful of historians, so it would need to rebuild its support from square one, just like a brand-new party would.
Please consider making this change? Thank you!