When do you change your sewing needle?

I was just wondering how often to change my needle.  Every project?  My manuel doesn't really give me a guideline, just explains how to change it. 
Thanks

I usually change mine every project unless it was a really small project.  I find that most problems with my machine can be solved by changing the needle, so I like to keep a fresh one on there.

I heard you should change when you start a new project too.

I decided to change after breaking one off in my finger the other day... hehehe 
Wasn't as bad as it sounds. 

Paula x

I change mine every 4-8 hours of sewing along with changing it with different materials. Each time I change the needle, I also clean the lint out of machine.

If I'm sewing knits I change my needle very frequently, like after every 2 projects or so (project being a t-shirt, or baby pants and shirt).

For wovens I don't change the needle quite as often. Maybe I should change my needle today.

Looks like I don't change my needle enough!
But if there ever is a problem with my sewing (snags, bad tension etc) I always change a my needle and it fixes about 90% of problems.

I just go by feel.  You can usually tell when it needs changing...your needle doesn't move like it should through the fabric.

I change mine any time I change the type of fabric.  I probably don't change it enough.  I've sewn for
40 years and still get confused as to what size needle to use especially with 70, 80, or 90. 
I stay in these ranges.  I use a jean or leather needle when needed, especially when sewing through thick
layers.  I use ballpoint when sewing on knits.

A good rule of thumb is to change with every project but I'm cheap and wait for these tell-tale signs:
1.  A popping sound whenever the needle hits the fabric.
2.  When bobbin thread tangles or skips a stitch.
3.  When the stitches start to look uneven or pop up (just plain ugly).

Any of these or when I start to get frustrated and can't figure out why...I change the needle.  It makes the world of difference. 

Um, well, I have been breaking a lot of needles lately... so I change it when it breaks! Maybe it has something to do with I have been lazy and sewing over my pins instead of taking them out - ha ha!

Huh.  I'm guessing I'm not doing it enough.  I never realized that it could make that big of a difference.  I'm off to change my needle!!!

Thanks for the tips! I've been a baaaad girl and had the same needle since January. Don't throw things at me, I'm still new! Haha. I changed it the other day and MAN! There is a difference!

eeek. I need to change my needle more often! I've been using the same one for at least three projects, probably more, including curtains!

I agree with many others... I change my needle between projects. I'm a quilter that usually makes bed size quilts, so that's quilte a bit of sewing time between needle changes! Along with the needle change, I usually clean out the lint around the needle and bobbin case and put a drop of oil on the race which is in the bobbin shuttle area.

I just encountered a huge problem with my sewing machine last night and my first thought was that I might need to replace the needle--thanks for posting this question! I am a sewing novice, so I need lots of help and advice!