Typically, how often do most of you, change line and do you have a system for keeping track of how old and what size and brand and or type (mono or flouro) of line you have on each rod?

When I break off so much that I start to get a slow retrieve from lack of line on the spool....or a huge backlash. Whichever comes first. Lol.

Once very few months. Floro-Seaguar red label or invisx, mono-Big game or McCoy, braid-power pro

Seriously though....my new Lews reels have a line indicator dial on the tension knob that I set to remind me that I have 12lb Seagaur on the reels. (I have 12 pound InvisX on every reel but 3). As for when to change? My sarcastic post above isn't too far off.

About once a year. Keep rods inside unless fishing.

I use colored electrical tape around the butt of rod so that with a quick glance I know what line size is on that combo. Red = 10 lb, Blue = 15 lb, Green = 20 lb
This covers how I fish and I just change out as needed.

You could put a small sticker under the reel seat, and label line type/size and date

I bought a label machine....and I put

"20FL"
"8/30/16"

in a very small font and the label will stick to the side of the reel or underneath the handle....that way there is never a questions what I have on the reel and when I strung it.

Braid main line to different leaders on all rods (except crig) has worked well for me.

I change out the leaders when I see or feel significant abrasion damage; so I change the leader on my flipping and jig rods as frequently as once every 3 weeks.

My crig rod is fluoro mainline to copoly leader. It gets changed when I see coiling or abrasion in the main line or abrasion in the leader; so I change those out about every four months or so. (don't throw crig often)

Over winter, I'll reverse the braid mainline.

Change my primary reels once a month.

The Carbon-lite rods have a dial for line size. I always do a check on my line by tying a half hitch, cinching it and pulling on it. If it breaks its time to replace.

Use a permanent marker and write it on the reel myself. I don't date it. You can see when you need more line. Don't over complicate things... I'm not a huge tournament guy, so I use the same line for 6-12 months on many reels and never had an issue.

Change Fluor every 2-4 depending on which rod it is and braid I never change it, seems like it lasts forever

This ... and I write the date on the tape with a Sharpie so I know how old it is. I typically change my line quarterly. Breaking off makes me crazy and changing the line quarterly keeps it fresh enough to not be able to use the "bad line" excuse.

I don't change too often.. maybe once every few months. When I notice my casting distance is getting shortened because of the line kinking or if my spool is low, then I'll change it.