How often do you change? Needle and cutter Q. Sewing Machines Parts and Sales in Los Angeles

How often do you change your sewing machine needle?
How often do you change your rotary cutter blade?

Yeah, I know, when they get dull, toss ’em but how can you tell? How do you know?

Needles. When I’m sewing swim suits, I put in a new ball point needle with every suit and I toss the old one out. But, otherwise, I think I keep my needle in too long. When you switch from ball point to regular or back, do you ever re-use old needles or just toss them out?

Cutters. I’m relatively new to rotary cutters. I get that when it starts chewing up the fabric, it’s time to change but is there a set interval? Do you put in a new blade fairly often or only once in a while? I use mine to cut woven and knits. And I probably use it at least a little every day. Say, maybe a 10 to 15 minutes of cutting. If everything is average, how long should I use a blade for? A month? Less? Am I over thinking?