If you're not keeping your node onoine then you're going to have to start it at least as often as the timelock runs out for the channel (you can verify this number from its stats). If you don't put your channel back online before this time is up, there's a chance the other party can claim your funds afaik.
The other party cannot claim your funds just like that. There is a chance that the other party might broadcast an old commitment transaction. Once that happens then you have to come back online before the timelock expires and broadcast a penalty transaction. If you trust the node you are connected to then you can stay offline for as much as you want. You can also set up a watchtower which can automatically publish a penalty transaction for you.
Electrum founds channels with a to_self_delay of 1024 blocks (~1 week), so this means that you can be safely offline for slightly less than a week. As for now, this value can be only changed
directly in the code.
If your node remains online then you're contributing your channel funds to help route other people's transactions. The more channels you have open the more routing you can do also.
As nc50lc has said, channels founded using Electrum cannot be used for payment routing. All channels are private so they are not advertised across the network and cannot be found using Lightning explorers (ex.
1ml.com).
