I put the cash in MM fund and reinvest it into the same index fund when there's a drop. A bit of market timing if you well. I rarely do this except when the market has a huge run up that recently. I think I've done it maybe 4-5 times over the last 10 years. I can't really say I would have done better or worse had I stayed in the market full-time, so I guess motivation is mostly it's psychological.Curious. What do you reinvest in or do you keep the cash sitting in your account? My issue would be where to reinvest to continue growth.
The funny thing is I likely won't ever need to draw from my retirement accounts, so this exercise is really academic at the end of the day.