I have never mined any cryptocurrency and know nothing about the market or how the earnings from mining fluctuate, but I do have my computer turned on a lot of hours a day while studying, watching series or simply wasting time on Facebook. My computer is an hp laptop with a core i5 2540M processor, no dedicated gpu and 10 gigs of ram running windows 7 (I know, I'm about to update to 8.1). Would it be worth it to have it mine something on the background while I use it or would it just deteriorate it for no reason while not even matching the increased electricity consumption cost?
It is unlikely you would make any profit CPU mining unless you have free electricity. Even then the potential for shortening the life of your laptop would likely reduce profitability. There are a few altcoins that aim to allow people to mine with a CPU but its unlikely you will make more than a few cents per day.
Mining on the laptop will make the CPU operate at 100% capacity all the time. This will increase the temperature, decrease the battery life and increase the noise of the laptop (fans speed up as it gets hotter). Overall its likely you increase the chance of the laptop breaking as well.