I've had my iBook for almost 7 years now. Yes, it's so old it's a iBook, rather than a MacBook.
One of the best things these computer people invented was the sleep mode. It has essentially meant that I only switch my computer off every... I don't know.... 2-3 months when it's running too slow. No exaggeration. What can I say - I like lift the lid and start surfing immediately - no waiting for the computer to boot business.
And no, it's not bad for the computer - if it was surely it would have conked out by now? These computers were built to last I say, and be abused.
Here's my trusty old friend, with its pulsating white light. I always like to think that it's its way of showing that it's snoring. Very very gently.