so do I have to play custom games for 50 hours nonstop or can I just take breaks?
It’s a cumulative amount so you can take breaks. Once you hit 50 hours, you might have to wait a couple of days since the program or whatever that scans for players who should receive the helmet only checks once or twice a week.
I always wondered how I got the helmet. This explains a lot 
Yes you can take breaks! I’m 12 hours away from getting it!
9 Actually
The time playing multiplayer custom games on Halo 5 Forge PC counts also. I got it that way.
If you enjoy customs im sure you’ll get it in no time
You can take breaks it’s just a total of 50 hours of custom games altogether
Its 50 hours in total and not all at once if you look around a bunch of spartan companies throw a customs night mine does it every thursday 9pm ct i believe and is open to anyone just messagae shadowbmd and ask for a invite we have lots of fun average players are around a diamond