I use Bitcoin only on rare occasions - say once every month. I want to avoid long waiting times for downloading and verifying blocks that consequently await me when I reopen bitcoin-qt. There are many options available for downloading the whole block chain when one starts out (like the blockchain torrent or the blockchain on Sourceforge). However, these options are full of warnings that tell you they should NOT be used when updating the block chain on an existing wallet but rather only when installing from scratch.

Are there similar ways of more quickly updating the blockchain by downloading recent blocks from some other source?

Note: I am not looking for other clients, but specifically for alternative blockchain download options for bitcoin-qt.