I create Template for switch with 8 host items + (16LLD items + 3 graphs) per port. For first test I disable 50% items&graphs. Then I bind template to ~300 hosts/switches (every have 10/18/28 ports). Really I have ~50k enabled and ~70k disabled items.

And I got "Less than 25% free in the configuration cache" and same for trends. I delete disabled items from template and cache load falls down. Looks like Zabbix caching disabled items. Are it's really true? Maybe Zabbix don't need caching and think about disabled items at all? It can be option feature for memory (and CPU when do cache search) optimization.