6 months is for continuous residence requirement which is important for N-400. You should not have any trip exceeding 6 months at any point as GC holder, otherwise you'd break continuous residence for naturalization purposes. Say, today you returned from a 6.5 months trip overseas. This means you start counting eligibility date for N-400 from today, not when your GC started. So it would be 3 or 5 years from today. If you go again for over 6 months, your "clock" will reset again.
If you do a lot of trips such as 4 months out, two weeks in, you'll eventually find a CBP who will give you NTA or ask to sign I-407.
You should not be absent from the US for over 1 year at a time also. This could result in losing LPR status. Again, the "clock" resets, again CBP may conclude you abandoned LPR status.
Even if you don't spend more than 6 months or 1 year at a time, if you travel back and forth, don't forget for N-400 you need to spend at least 50% of the time in the US. And you'll have to provide all trip dates. So start keeping track of trips and countries visited in Excel / Google sheet. E.g. when you left, when you came back and what countries you visited.
Don't spend too much time outside of the US, as I-751 would be harder to approve with no ties / jobs / lease in the US.
You should at least maintain bank accounts and lease in the US do demonstrate some ties. If you don't keep ties and use GC as fancy visa instead of living in the US, you will lose residency and won't be able to naturalize.