You gave a pretty well rounded answer, thank you for that. Though, it, too, seems to address device risk more than the risk to reward ratio of keeping the wallet open for staking 24/7 (in the context of a device that is kept connected to the internet 24/7 anyway, for reasons other than staking). If there is a hack attack or malware infection, seems to me that can happen at any time that the wallet is staking, even if it is only staking, say, one hour per day. And, although obviously the risk from hacking or malware increases the longer the wallet is kept open, so do the staking rewards - hence why the question is about risk/reward ratio, not just increased risk.
The only difference between staking and not staking is that it's connected to the internet. I addressed the probability of being "hacked" via the internet, which is pretty low IMO, as long as no other services are running on your system that would be prone to security issues. It really depends on your system then.
About the only thing you mentioned that seemed to me to pose increased risk vs. reward, is the possibility of the device, with the wallet on it, being stolen; the risk of burglary is certainly higher at certain times of the day (or night). Though, during staking the wallet is unlocked for staking only, and if I am not mistaken, the pass phrase would still be needed in order to access the funds on the wallet. Is there a possibility that a thief could quickly bypass the pass phrase through hacking? Seems to me that if one keeps a recent copy of the wallet.dat on file (on a different device or medium, stored in a separate location), one's funds would be pretty secure even in the event that the device is stolen without an interruption of the power supply, even while the wallet is unlocked for staking - but I am no tech expert by any means.
Sounds about right. If you use a strong password to encrypt your wallet, then local attacks are negligible.
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