Just so you know I am definitely not anti Gibson ....
Yup - well this is what the 'market' has been screaming for/at Gibson for years - and be careful what you wish for. "Thinner thinner thinner thinner.... Nitro nitro nitro...." Most of the people screaming this stuff have heard or read pseudo-science that "thinner finishes" equal " more 'tone' " whatever that means. And there's some romantic throw-back advantage to a finish that has been improved upon 1000 times over the past 50 years. So now... combine razor-thin fluid finishes with less-than-ideal lumber (the kind of old-growth wood available in 1950s and earlier is long-gone) and you're going to get very unpredictable finishes. 6 months doesn't surprise me at all... not *at all*. I'm surprised you didn't notice changes much sooner in fact.
Now a couple words of good news for you... 1) LIke others have mentioned, these cracky/finicky 'road worn' relic'd finishes are what everyone wants - so it's not going to reduce the value of your guitars at all IMO. Advertise them "beautiful natural relic'd patina..." or similar and you'll get hoards of buyers. 2) It's not that big a deal to re-spray the clear coats on these instruments. Since there isn't much finish on them to begin with, a good shop can mux all the cracking together with a combo of sanding/solvents and then re-spray more nitro... doing the mechanical buffing/etc. It'll cost you a cpl hundred bucks for each guitar but the results might be worth it to you to start over with no checking. Unfortunately - doing *that* might in fact reduce the resale value because you've altered the guitar. I don't know - the market is very fickle. The sad thing is that if there was not this ridiculous rush to outdated finishes, Gibson could use clear finishes that would never crack or check (unless you did the -20 degree thing) and would look as good as new 20 yrs from now. I'm talking about modern polyester and urethane finishes which, IMO do not impact "tone" of a solidbody guitar *one iota*. But try to sell that to the guitar-voodoo masses... good luck with that.
JLS