The 30 days Coin-age is the minimal requirement for the POS to work.

Before that, you simply need to leave those PACs in the old wallet clients (without being spent) to accumulate the coin-age. Certainly, you should at least run the old wallet client at times to get the wallet sync'd but POS staking won't start until the time some of the PAC balances have the coin-age of 30 days or so.

After 30 days, you can keep your old PAC wallet client running for POS which is about 7-9% per month or 100% per year.

It is unclear how long it take for you to get the POS of this % of minting rewards you are entitled to. I bet that one week may or may not be enough and 2 weeks are probably better. Let's say that, at the end of 15 days of POS, most of the coins with coin-age starting with 30 days at the beginning would have their coin-age "spent" and the corresponding coin-age would have been reset and started with a new count. There might be a very small amount of PACs still not having their coin-age spent through minting rewards during those days (31-45th), and these would have a coin-age of 46 days. Whatever PAC's coin-age spent during the last 15 days, would now have the coin-age of 1-15 days. It is a dynamic process and never ending.

In short, you can always keep the old PAC wallet running for POS minting to get those 7-9% per month of POS rewards until right before the next 1:2000 swap ratio kicks in in June 2018. And you would have up to 4 months worth of POS rewards, close to 30% or more, (remembering that you always start with one month of coin-age already.)