Ability to Send Bitcoins to an Address over a duration of time
Seems like you're looking for an automated billing solution, or something along those lines. There may be others, but I know Coinbase has support for this. This is a screen shot from their online interface:







If it was a recurring payment in small amounts, you might also consider Micropayment Channels, so that the feels were not prohibitive. For larger, monthly or yearly transactions, though, the fees paid to the miners may not be as noticeable.