Assuming that your issue is with wanting a longer battery, and not just from wanting longer charge cables, there is a fairly simple way to double the DS4's battery life.

I haven't tried swapping out a battery pack, but the DS4 is definitely the easiest controller to get into and modify (I've made it all the way to taking apart the touchpad for a simple ribbon repair). A handful of small phillips screws, and it's at your mercy..

The battery life of the DS4 is just so bad. I can burn through it with a decent session. My Xbox One controller with rechargeable Eneloops lasted literally for weeks. They're not even in the same universe.

My biggest issue was that, no matter which combination of plugs and cables I used, the DS4 would not charge from any source besides the PS4 itself, meaning I always had to get up to plug it in, and I didn't have a cable anywhere near long enough to play while it was plugged in, and I would often just be too lazy to get up and plug it in when I was done playing. First world problems, I know. But compared to just swapping in a new set of rechargeable AAs every few weeks with the Xbox One, it was definitely super annoying. I largely fixed the problem by getting a charging station that is on my night stand so I can just drop the DS4 on that when I'm done and it's fully charged and ready to go the next time I pick it up. It's been fine so far, but I can still get awfully close to depleting the battery on a decent binge (it really only seems to take a few hours).

I would definitely consider swapping in a bigger battery, by its not been enough of an issue lately for me to go through the effort. I'm bookmarking that thread to keep it handy, though!

I bought one of those Energizer recharging stands that holds and charges 2 DS4 controllers. I keep my controllers in the stand whenever I'm not using them so they're always fully charged, and if I manage to kill the battery in one of them over the course of a single play session, I just throw it in the stand and grab the other one.

Energizer makes a stand for Xbox One controllers, too (which I also have). It comes with rechargeable packs that go into the controllers, and a replacement cover with a port in it so you can charge the controllers just by slipping them into the stand. Works beautifully well.

* Pro tip *

You may have done this already, but you can reduce the brightness of the LED on the DS4, which helps out with the battery life.