"All retirement-eligible employees working full time in federal service for the previous three years are eligible for phased retirement, OPM said, though the agency must consent to the arrangement. An employee 'does not have an entitlement' to partially retire.... These employees will receive half of the normal pay of the position, as well as half their normal retirement annuity.... Most other benefits -- such as health benefits, the Federal Employee Group Life Insurance benefit, survivor benefits and annuity garnishment protection -- are calculated as if the partial retiree were still a full-time employee."