After that, you peen the lock spring to make it longer, have a new liner made, or retire your knife.
Titanium will wear pretty fast, but it doesn't necessarily mean within your lifetime. Lotta variables.
If I were in your situation, I'd use it until it wears out years or decades from now. Then peen until that option is exhausted. By then, if I still didn't want to send it in to get it back to factory spec, I'd have a new locking liner made using the old one as a template, only made out of steel.
The steel will most likely NEVER wear out within your lifetime.