if maintenance wasn't permanent, games would go on forever because destroying ships would pretty much be meaningles
My experience has been the exact opposite - this game mechanic makes games take much, much longer, because the costs for upgrading your upkeep is so prohibitively high. You just cannot afford to upgrade your upkeep to any amount without first maxing out your economic production and saving up as much as you can in hopes it will be enough before you bite the bullet.
Starbases help with this incentive to turtle it out for as long as possible - requiring no unkeep and once upgraded can be very costly to attack.
And if you have an ally as a TEC player for example, it gives even more incentive for the TEC to spend the first hours of the game building up economy. You simply take your ally's natural expansion planets/asteroids and tribute your resources to an ally who has maxed out the upkeep researches, thus circumventing the upkeep mechanism.
Furthermore, the TEC player has even more incentive to turtle while he/she waits for the Supply Pact to become available with the ally - problem being that again this takes a long time to get.
This is my biggest single issue with the game. You sacrifice too much by upgrading your upkeep. You need to build up your economy and save for hours before you can afford to upgrade it.
The incentives for early game brawls would be much greater with a variable upkeep rate, based on your current fleet usage. It can be per-ship or have different upkeep population brackets. Although the gameplay for each RTS is different, virtually all the other RTS games I'm familiar with that have upkeep penalties successfully use a variable upkeep model rather than a fixed upkeep like Sins (Warcraft III is one example).
At the least I would highly recommend this at least be an option for the game - just a tickbox for "Variable Upkeep" for those that want to play with variable upkeep vs. the current system.
