A lot and basically because I can't be bothered to put what someone else has already said.

The Bird of Hermes is my name, eating my wings to make me tame.

Does TC even know what "frequently" means?

Not often.
I don't want to waste the time I had spent typing something just to end up not posting anything.

As soon as I hit post reply, and start typing. At some point or another I end up hitting submit reply.

The only times I hit cancel reply is if I haven't typed anything yet, or had second & third thoughts whether I should express my opinion or not.

Yes yes, I know I make longwinded comments, but that's just me >.<
I should proof read my comments more, but I won't...
So keep in mind I'm filled with typos

Check out FAQ and Forum Rules if you haven't yet.
For errors linking in threads

Oh God, I do this way too much, but the problem is that I don't "cancel it half-way through". Oh, no, no, no... I'll write a full length post, clean it of any errors, make sure it's worded juuuuust the way I want it... and then not post it.

I think I have around 30 full posts I never made saved into wordpad, including one that's around 25 pages long, and probably another 30+ I just outright canceled without saving.

Trust me, it's... better this way.

I infrequently post on them although I have no idea what they're talking about since it like many many pages long and many many conversations at once. But sometime I cancel it and other times I actually respond to it.

Owner of Tainted Sins & Forgotten Scans
Head Manager of Happy Tea Scans

All the freaking time. Either I realize halfway through that what I was going to say isn't necessary, I misunderstood the topic or I just give up for some other reason.