1. If you loose your online redo logs as well then you can't recover your database "fully". Transactions recorded in online redo logs can not be revoverd if you lost them before it has been archived.

2. You do not backup your online redo log files during hotbackup.

3. You don't have to keep the archived log files after a successful hotback unless you want a PITR before that successful hotbackup.

Sanjay