Deluge has this nice plugin called scheduler that let’s you program at which time the torrents should download/seed, if you have a small homeserver on something such as a raspberry pi you can just schedule deluge to work when you’re asleep, this way you can seed/download while not impacting your bandwidth when you need it, very useful to really slow connections (like mine).
This way you can keep seeding for months without even noticing!
I’ve been maxing out my upload (only 30 mbit…) and my ISP hasn’t complained at all.
I guess it varies between ISPs but mine has written to me a couple of times in the past to give me “gentle reminders” not to download “vast quantities of data” during peak hours. :P