Persistency

By this hand thou, thinkeſt me as farre in the diuels booke, as thou and Falſtaffe, for obduracie and perſiſtancie, let the end trie the man, [...]

Source: wiktionary

On entering her room he had been struck by the absence of that saucy independence usually apparent in her bearing towards him, notwithstanding the persistency with which he had hovered near her for the previous month.

Source: wiktionary

However that may be, the hostility of the comic writers had evidently a general hostility behind it. Our tradition states this definitely and the persistency of the attacks proves it.

Source: wiktionary

"I'm not into mood changes," he says. "These ups and downs undermine consistency and persistency of purpose."

Source: wiktionary