Hey, @ltetak.
I’m not sure why you wouldn’t know that. You did the same in the past already.
Not touching your structure for 30 days will mean it’ll be deleted.
If you know you’ll be away from your structures for a long time, you can buy this package, for long-term saving (but not across a full wipe) 
I will restore your structures for you, but next time we won’t be able to help with this exact issue.