[md1515]

A few things to think about:

1) You are still growing quite rapidly, so you need to be wary of killing off that growth. I think your method of giving ~3 months usage free will go a long way in retaining that growth

2) I don't think it is too expensive on a yearly basis, but maybe give them a discount if they pay by the year? Even if it is a couple bucks. They will already be inclined to pay for the full year because it isn't that expensive and $2.40 is a hassle to pay every month. Give them an additional reason to stay with you the entire year.

Good luck