This is most likely NOT discrimination, since  in regards to insurance policies and other benefits (like pensions, 401ks, etc. for example), it has long been accepted that these benefits may be age-based in terms of eligibility, premiums, how and when paid out, etc. The fact that your employer may provide or make available to you certain insurance or benefits does not your ineligiblity for them, under the usual rules governing said insurance or benefits, into illegal age discrimation; the laws governing the policy or benefit are what counts for ths purpose, not employment discrimination law.