Reply S1 Visa renewal and work permit visa renewal

My wife is accompanying me in China with a S1 and it is about to expire in August. My work permit will be extended by my company but I have to extend/ renew my wife's residents permit privately. The new rule states that all work permit extensions must be submitted a month before the expiry date. Now my question is I will have to submit my passport in before end of July, but my wife's one doesn't need be submitted that early...so without knowing an exact expiry date on my work permit how can I submit my my wife's application form ? because in the application form and the request letter I have to mention a date to say how long I need the S1 to (which will be my work permits expiry date) ??? sometimes the PSB takes more than a few days to return the passport so I am in a little dilema...any help will be highly appreciated.