I never played Guildwars 2, but a quick read on the gameplay structure reminds me of Dark Age of Camelot. That game did not have staying power for the same reasons that Planetside 2 lacks it; neither game has long term progression. They both allow fighting over a set of terrain, and wins never mean anything of consequence.
A game with real staying power is one where not only are there wins to be had, but there are cumulative wins. Wins that are not discarded, and made irrelevant at the whim of the game designers. “Well, you fought tooth and nail to win that one, and you’ve got some good memories out of it - so let’s wipe out all traces of it and start over.”
Instead, have the players spend a few hours fighting to control a space station. That space station allows the winners to control some resource that alters the way their team plays the game. In-game command and control systems. Multispectral sensors. Jammers. Stuff like that. NOT better combat capabilities, just stuff that allows the players to play the game in ways that they couldn’t before.
Players want all that stuff so that they can win the system. That’s a cumulative goal that can take a day or a week or however long. There can be plenty of places and things to fight over and control before the system falls to one team or the other.
What then? Wipe the system and start over? Absolutely not. Leave it there. It is the memory anchor to let players take a trip down memory lane. Each system will have unique memories associated with it.
Winning a system is just like winning a station. The winners now have access to the system’s stuff, and that allows them to its long-range capabilities when they move to the next system - but only while in range. All the systems that they’ve conquered and that are within range add to the team’s capabilities. Some are just a check of either “in range” or “out of range” while other systems attenuate their capabilities based on distance. If a team is on the verge of losing an important capability from a distant system, they’re going to fight hard to get it back when it next hangs in the balance in a new system. Or fight hard to make sure the next system is still in range.
That means that teams have a natural tendency to try to conquer systems that are well-supported by their territory. The other team is trying to do the same thing. The victor of the last fight decides where the next fight is going to be, but the possible jump targets from the last-won system are limited. All of the next targets may benefit the other team, but you won’t know that until you’ve won the system.
The next design task is to create a cumulative progression system for the game that both teams go through. Start with small-scale gear in the first systems, and incrementally allow the teams to get into bigger and badder hardware with more complex gameplay involved. Instead of allowing individuals to gear up by grinding out accomplishments, allow both teams to progress through the game system bit by bit. It’s a bit like a reverse Ender’s Game.
Introduce the new gear in a procedural way such that no two games have the same progression sequence. Certainly the network of systems that the teams can fight through would be procedural.
That sort of a formula could carry on for months, perhaps a year. Players who like it at all will want to go through it all again. If a player wants to go through a given game experience three or four times before they get bored with it, then you’ve got a couple years of life from a pretty simple game structure. The most difficult part of this is coming up with the stuff through which the players can progress. If you can only afford to develop one class of ship and two weapon systems, it’s kinda difficult to provide any sense of progression over time; there just isn’t enough content.
Lastly, the trivial increments that most games present are not going to cut it here. Winning a system and getting a 1% upgrade in turret performance on one type of weapon system is the stuff of aggravating grinds. Each 10 systems or so should bring some significant change to gameplay. A new class of ship. Or a new weapon type (e.g. missiles, laser, mines, rockets, etc.) Or those multispectral sensors. Something big each time.