If I check server details https://www.earthempires.com/ai/serverdetails I can find:

Time on Market: Unsold goods stay on the market for 3 hours.

For most (all?) the other values on this page I can find a corresponding value in the Rules Class:

{
  "RULES": {
    "maxturns": "1900",
    "maxstore": "360",
    "is_clan_server": 1,
    "is_oil_on_pm": false,
    "base_pm_food_sell_price": 32,
    "max_time_to_market": 1080,
    "max_possible_market_sell": 45,
    "market_autobuy_tech_price": 900,
    "custom_market_times_allowed": false,
    "min_seconds_for_custom_market_time": 0,
    "max_seconds_for_custom_market_time": 0,
    "change_set": 22,
    "ingame_def_allies_allowed": true,
    "ingame_off_allies_allowed": true,
    "ingame_res_allies_allowed": true,
    "ingame_spy_allies_allowed": true,
    "ingame_trade_allies_allowed": true
  }
}

I am wondering if there should be a "max_time_on_market": 10800