My computer doesn't work, so I will not be able to play League of Legends again for some months. Will Riot delete my account because of inactivity?
They will not remove your account:
Will I lose my content if my account becomes inactive?
No! Account content (Champions, Skins, RP, etc) can never be lost through inactivity. Only your Summoner Name will be affected.
However, you will loose League Points (LP) and maybe even ranks. Your name can also become available to be claimed after 6 + (each summoner level above 6) months.