At least four days before you leave, end all your current listings.
They will go into your Unsold List and stay there for 90 days.
When you return, Relist all your items. Or use Sell Similar.
Yes, you will pay another fee and yes, you are "wasting" the fees you already spent, but think of how much trouble a single unhappy buyer who didn't read your warning carefully can cause.
The four days is because if someone bids and doesn't pay promptly, you have 4 days (96 hours) to open an Unpaid Item Dispute.