I do this with the secret email that I use specifically for Runescape on both of my accounts.
It's good to create a new email with a hard to guess address and super tough password, plus a security key. This way, if I receive an email on it from anyone besides Jagex/Runescape - it means that my email has been logged somewhere else, which is not what I want. Versus using my primary account that gets dozens of emails everyday.