Wife (teacher) has 100% allocated to an 8% fixed return plan. Should I swap to 100% S&P in one shot, April 1st, or gradually over 12 months? 20 years to go before retirement.

This was not an ideal decision when the plan was set up and she was advised by her father, but it is what it is now - and it's time to fix it. She missed out on some serious gains over the last 15+ years, but at least the 401k was maxed out every year.

Curious to know the community's thoughts -- especially given the market these days.

I recognize that no one has a crystal ball. She likely has another 20 years to go before retiring officially.

Edit: The available plan options are pretty awful.