In our case we just don't have that kind of cash lying around. If it isn't bolted down it goes into an account. Instead I spend some time at the end of December tosetup all the assorted accounts to hit my annual goal by the end of the year. Everything else spare goes into the taxable (also setup to automatically hit my minimum savings goal for the year).
My friend has what he calls "Andy Luck Factor" where everything he touches turns to gold. A number of years back he had read too much Zero Hedge and decided he needed a backup plan for when America fell apart. He ended up putting all his money into New Zealand CD's to help establish a backup permanent residency and ended up making >50% on exchange rate fluctuations without even intending to in less than 2 years. He retired to Montana where he lives in a "toy box", which is an apartment over a hangar with his plane, Lotus, and 1978 Land Cruiser.
I have the opposite luck. My experience is that every time my savings account exceeds $5k something bad will happen to use it up. Last year it was a leaky roof, before that some major vet bills, etc, etc. I bought our house at the absolute peak of the local market in 2007 as well. Somehow the bad luck trigger has not spilled over to my brokerage account, so I shovel money into it before I get to that stupid $5k bad luck trigger point. So having a pile of automatic transfers to 401k/IRA/Roth/529/Taxable keeps as much money as I can spare in the market at all times I probably should be prioritizing these and knocking out the spousal IRA before the Roth, but I am a fan of simple and automatic.
Paranoid? Yes. Works for me however.