How far have you gotten on endless mode?

I too got into the mid-20's and then started getting sloppy until I died. Like Draikan said, eventually you get a bunch of lasers/death rays that torch your fleet instantly. It's against celestials or unknowns. The only way to fight it is to distress beacon all the time and attack enemies while they're still charging up their weapons after warping in, but it's an incredibly tedious way to play... you have to do it all the time since you don't know if the 3 ships in the next area have 6 death rays or 6 ion cannons, so you have to expect the worst.