TIPS are easily traded on secondary markets. In addition, there are multiple TIPS-backed ETFs [0] that trade in extremely high volume. I guarantee you could exchange TIP shares for USD in seconds, not minutes.
You can sell TIPS on the secondary market whenever you want, and you can redeem I-Bonds directly with the treasury after one year. The only delay is the electronic transfer to your bank account from your broker or the treasury.
[0] http://www.investopedia.com/articles/investing/092215/top-5-...