Trust me, if you manage to get in 1500+ years (I have) repeatable tech decides everything, the galaxy becomes a bloodbath, and surprisingly if you protect smaller empires, they out tech larger one even without research agreements, resulting in a swarm of mini empires akin to fallen empires in strength

. I just sat in my corner and watched, eventually one empire won and basically flatten the whole galaxy except me.
However I'd gotten so far with repeatable tech a single battleship of mine reach 700,000 fleet strength, the lances just never stopped firing (basically no weapon cool down) and a single ring world system produced all I needed (including science)
After a while I just declared war and started cleansing all of his planets, with my borders expanding each time I did. Eventually his empire was dead and I owned the whole galaxy whilst only populating a single ringworld.
Bet you few people have ended a play through like that