We clip about every 10 days for two reasons, our safety and theirs.
Bijou likes to knead my face and neck while he has his little "suckle" before bedtime and if I didn't clip nails, can you just imagine what I'd look like!
He also got his nails caught in something one time and ended up having 2 of them bleeding which I'm assuming was caused by his efforts to free himself. I've also seen him get them caught in the screen door.
I use human clippers but I turn them and cut from the side which seems to make a cleaner cut. I basically just clip the shart point before the red line.
If you start them young, they get used to it and although I don't think they ever learn to like it, they tolerate it and always get a treat afterwards.