What is Extra compensation or extra benefits are we to give workers working for 25-30 years?

We have permanent & casual workers whose working period is more that 15 to 20 Years.Now issue is that they not accepted a new worker in company premises & try to misguide new person.Management is asking that give them the notice pay,gratuity, leave encashment & ask them to leave.
1. But they are threat us the labor advocate that what the extra benefits we get after working so much year ?
2. what the extra benefits they eligible by law or any human rights ?
3. They saying that we have given our whole life. One employee is working from 25 to 30 Years having age of 60 above.
What the legal compliance fall & how we tackle it.
4. Some not get the epf benefits cause we are exempted employment have the required docs. Are we fall in the not follow the any fund deduction epf etc.
request you to please answer one by one point.
your comment will help us to understand & follow the things more efficiently.

As per ID Act 15 days wages for every completed year of service, but in practice, some companies considering smooth / quick settlement of claim in an IR situation paid up to 45 days wages. Gratuity 15 days wages for every completed year of service, Leave salary, Notice Pay all put together,Based on the viability and available / allotted funds, you are the best judge and as a best negotiator decide a best package and enter into an settlement under section 12(3) of the ID Act.
Best of Luck