Of course they do.
If you stay more than 6 months outside the U.S. and without a reentry permit, you will break you continuous residency and lose your GC.
Staying 5 months out every year will raise big flags to the CBP officers at the port of entry and they may think that you are abandoning your U.S. residency.
I hope you are filling your taxes every year and keeping some sort of ties to the U.S. such as rent, properties, family, etc..
I assumed that you are not planning to apply for U.S. citizenship anytime soon... because those 5 months are added to your 5 years application elegibility clock. So if you are thinking in apply for your U.S. citizenship at the 5 years after your GC issuance date, you have to add all the days you have been out of the U.S. and that will give you your new application date.