Here are the current lifetime requirements for Silver, Gold, and Platinum:
• Platinum Elite: 750 nights + 2 million points
• Gold Elite: 500 nights + 1.6 million points
• Silver Elite: 250 nights + 1.2 million points
Please contact Marriott Rewards customer service either via phone or email to get your lifetime point total.
I agree that it would be nice to have the lifetime point total on the website, and I will suggest it. The only two reasons I can think of that would prevent it from happening (and are perhaps the reasons why it's not in place already) are:
1) System availability - I know that the MR agents currently have to manually add the current balance and redeemed together.
2) I would be concerned that the display of lifetime points would be mistaken for current balance.