Can I Send Additional Money to a DRIP at Any Time?
Q. Do DRIPs have a specific requirement that I invest money on a monthly/quarterly basis, or can I send additional money when I have the dollars?
A. You don't have to commit to a regular monthly or quarterly purchase in a DRIP; you can make purchases whenever you have the cash.
Of course, the purchase date is determined by the DRIP administrator; purchases are only made on that specified monhtly, quarterly, or other regular date.
Some DRIPs offer an automatic investing plan, where you can have money transferred from your bank account each month and invested in new purchases automatically. These plans have the added advantage of allowing you to utilize "dollar-cost averaging" in which your set regular investment will purchase fewer shares when the price is high and more shares when the price is low.