Yup... It's the classic rent or buy scenario...Biggest benefit is typically you can recoup most of your "investment" if you purchase Lifetime if/when you sell your TiVo.
If you buy your box for $100.00 and subscribe to the annual service and pay for three years, your box would be worth no more than $100 minus depreciation of the box. Everything you put in to the service evaporates.
If you buy the box for $100.00, and buy the All-In-Service for $500.00...the service is connected to the box and the resale value would factor this in...
As an example, I just sold my TiVo Roamio Pro (with the All-In-Service) for $429.99 on eBay last year.