Yes, 24/7. Just open the wallet, unlock it (for staking only), minimise it and forget about it. It uses very few resources and will continue earning you rewards in the background.

What staking rewards were you expecting? Or are you talking about Masternode rewards (which are much higher)?

What you have to remember is that with simple staking you're making money for doing nothing and you're free to spend your stake at any time. While there's a risk, due to price volatility (as with any cryptocurrency), that your original investment may lose value, it's not like the investment is 'spent' (like it is with a hardware investment, for example). The return you receive is actually in addition to your investment (compounded) rather than a payback of your investment. If my calculations are correct, an investment of $1000 could grow by $200 or more per year. Personally I think that's pretty good. Show me a bank account that gives returns anywhere near that for such a small investment.

I also think the return on investment is about right and I would avoid any coin that had much higher returns. If the return is too high it devalues the coin because it quickly increases the amount of coins in circulation. Therefore, much higher returns are unsustainable and are usually a sign that the coin is poorly designed or is some sort of scam.