They announce the next year's dues in the notice of the annual meeting which is sent in mid/late November. The actual statements come in late December. If you pay on the first of the month, they change it to the 15th for January only so that they have time to process the new dues.
The dues amounts do change from year to year. I joined in 1999 (BWV) and they went down a little in 2000 & 2001 and went up a little in 2002 & 2003. The increase in 2002 was 10 cents a point, in 2003 18 cents.
They do not charge anything to pay monthly. One advantage to pay in full is if you have a credit card that has rewards, you can charge the full amount in January and get reward points. For monthly payments, they only accept an automatic debit from a bank account, no credit cards.