Yep... I don't pay for my electricity at home, it's a part of my fixed rent. So I utilize what I can by having my old Athalon X2 64 machines, and early generation i5/i7 laptops/machines running with extra forced-air cooling.... Typically I wouldn't do it.... but there are some scenarios. It's nice getting a steady trickle of 0.00000015-0.000000105 all day on top of the bigger 0.000019 per block reward of the GPU coins my home miners bring in.
The secondary reason I run them especially in the winter is the heat =)
Winter is definitely the best season to mine any kind of cryptocurrency. You spend less effort and cost setting up cooling solutions, to keep your mining rig performing at optimum conditions. It is nice to put old PCs to good use, as you would be contributing to any CPU cryptocurrency's network security. I usually put up an old HP laptop I have lying around to mine CryptoNote coins like Bytecoin and Monero, as well as use the computers at college to do CPU mining in my spare time.
not a guaranteed profit, but mine many of the new coins that come out for a short period and then shut the wallet down, but keep it on the hard drive. new coins, wallet, data and all, sit at less than 10-50 mb. you can collect quite a few in short period and many newer coins can be mined for a couple days and produce 100,000 coins. if any of these hit an exchange and hit even 150 sat, then you have made a nice small profit.
Yeah. Even though mining these coins are not profitable, they are still fun to mine and hold up for the long term, in case it spikes in price sometime in the future. Since CPU mining is accessible from within almost any PC or mobile device, it is very ideal to secure CPU mineable cryptocurrencies, while at the same time earning some spare cash along the way.
Good old PCs are very useful for CPU mining, in my own opinion, as you can put them up to good use to secure cryptocurrencies, as well as getting the most money out of it. Just my thoughts.