Seasonal employee vs temporary employee vs permanent employee

Generally an employer may retain a "seasonal" employee indefinitely without providing benefits. However, the terms of the employer's benefit plans may trigger eligibility after some period of employment. You would need to review the plan documents or summary plan descriptions to determine potential eligibility. Also, under federal law (ERISA) employees employed more than 1000 hours in a 12 month period must be offered coverage under a company's retirement/401k plans.

I suggest you ask for the company's plan documents or summary plan descriptions and posssibly contact an attorney for help.