There is no number of post a week or day, you can post as much as you can it just that their is a waiting time between post, just like going through the messages properly before replying.
That's right, you can post as many times as you want during 24x7 but there's only waiting time between posts. Meanwhile you have a limit on the number of PMs you can send per hour or per day which may be different for each number of your current activity.
Here's a quote from theymos about PM limits.
| Activity | Max recipients | Max recipients if whitelisted | Max PMs per hour | Max PMs per hour if whitelisted | Max PMs per day | Max PMs per day if whitelisted |
| 0 | 2 | 10 | 1 | 40 | 2 | 120 |
| 15 | 3 | 10 | 10 | 40 | 15 | 120 |
| 30 | 5 | 10 | 10 | 40 | 30 | 120 |
| 100 | 7 | 14 | 20 | 80 | 150 | 600 |
| 250 | 15 | 30 | 120 | 120 | 300 | 1200 |
| 500 | 30 | 30 | 120 | 120 | 1200 | 1200 |