Blast ramp does not have a function to end a season.
We recommend two options:
1. Use the "Stop Selling" function under Mass Edit. This is done at SKU level.
2. Create a linelist called "ARCHIVE" and move all the SKUs into that ARCHIVE linelist. Then delete the original linelist name. Advanced > Administration > Portal Settings > Lineslists/Seasons - manage the product linelists/seasons available in blast ramp