I was using THC as shorthand, but yes, all THC in the flowers is THCa. It degrades to CBNa over time. It's the heat from the flame (or decarbed in the oven) that splits the acid molecule off. And though some acid molecules will split off on their own over time, I wouldn't advise just waiting a few years for your harvest to get you high rather than smoking them.Well the THCa in flowers turns to THC over time ,why wouldn't the ThCa in the trichome heads do the same thing?
I'm sure there is other things in trichome heads than just pure THC
In terms of what else is in the trichome head, there are a whole host of cannabinoids and terpenes in there. I don't know which ones get better with age, but volatile terpenes seem only to fade away over time.