A while back, I got into this little mental rut of wanting to post exactly 100 times per week. I thought that was a nice, steady number, and it worked out at roughly 15 posts per day - a large amount, but not unwieldy. Don't ask me how this got started, as I have no idea. Since then, however, the ideal has been dialled back considerably - while I do like to stay active, on the whole, I don't feel obliged to post 100 times per week if I don't want to. What has emerged from that, however, is that I now like to post in multiples of 5. Some days I'll make 5 new posts, other days will have 10 new ones, 15, and - on the rare occasion when I've got a lot to say - 20! Take my current post count (8,827): I'll probably post 3 more times tonight, and then call it a night for PC. It's not quite OCD, I don't think... there have been times where I've left the number as something very obscure (like 8,324) and I haven't killed myself. But I feel a lot more comfortable with a postcount ending in 5 or 0 when I go to bed.
On a more specific level, I like to post about once a day in C&M, just to make sure members think I have a presence there. But it usually results in more than one post a day with moving/locking/answering questions etc. So that I don't get accused of raping OVP, I try to limit myself to only posting there 5 times in one day. Most other boards that I go to, I try to make regular contributions, but not so that I don't drown the conversation. Unlike C&M, however, there's no real obligation on my part; I just like to post in a lot of places. If there's nothing for me to say in, say, PGC for that day, then I won't post anything. But if there is, I shall.