I change the needle at the beginning of a new project. This is a small amount of money to pay for good results.

Every new project, and I use a bigger needle to quilt with than I piece with so each project is two neeedles. Needles are cheap and easy to store.

Whenever you are having problems and just can't figure it out, start by replacing the needle. There could be a flaw in even a brand new one.

If you hear a pooka-pooka sound as you are sewing, that means your needle is beyond dull and needs to be replaced immediately.

I change mine when it starts making a louder noise than normal. I don't sew over pins but every now & then a needle of mine will break. I know I should change them more often but I just don't.

When it makes a noise.

Not nearly often enough. Usually when I break one. I need to be better about it.

When I can't remember the last time I changed it? I know that's bad, but unless I'm having trouble, I don't think about my needle till I give the machine a drop of oil. My dealer said her rule of thumb for when to add oil is when you think about it. I like to clean out lint from everything--sewing machine, dryer, clothes--so I really should train myself to be more vigilant about changing the needle. I do change it after finishing a big project because I won't remember when it comes to changing it before the next project--unless I remove it completely till I sew again.

With my iphone, I guess it should be easy enough to put a reminder on it. But how often? I would never keep track of every 8 hours.

No rhyme or reason for when I change, all of the above at the minimum. I do however use a small sticky note with the date and size of needle taped to my machine when I do change. Only takes a second to jot it on there and I don't have to guess or remember when was the last time and what size needle is it.

That is me too! Lol

I too am in the "not often enough" category. When I can "hear" the needle hitting the fabric I usually change it or, since I am one of those who sews over pins, if I have hit a pin squarely it gets changed immediately.

Only if I break or bend one. And of course if I need do go from a sharp to a ballpoint.