如何使RSS-feeds条目的可用时间长于从源可访问的条目？

My computer at home is set up to automatically download some stuff from RSS feeds (mostly torrents and podcasts). However, I don't always keep this computer on. The sites I subscribe to have a relatively large throughput, so when I turn the computer back on it has no idea what it missed between the the time it was turned off and the latest update. My computer at home is set up to automatically