This is not two more years of warranty (which covers defects from original assembly that don't show up in the first four years) but rather maintenance, which is to say scheduled services such as oil changes, etc. That is a lot of oil changes, and maybe a brake replacement.

I wouldn't buy any service package at time of purchase unless I knew that I would still have the vehicle after six years, that my selling dealer was the one I wanted to be doing the service work outside of the warranty period, that it was discounted from retail service prices, and if it wasn't available later. In other words, hardly ever.

You should be able to purchase this type of plan any time up to expiry of the standard plan, but ask your dealer to see if your local rules are the same. Only reason to buy it now is to include it in your bank loan, but if the vehicle is paid off you should be able to cover maintenance costs whether by pay as you go, or with a plan purchased later.

A separate question is whether you should buy an extended warranty, if it is available at time of purchase.

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2007 X3 3.0si, 6 MT, Premium, White

Retired:
2008 535i, 6 MT, M Sport, Premium, Space Grey
2003 X5 3.0 Steptronic, Premium, Titanium Silver
2002 325xi 5 MT, Steel Grey
2004 Z4 3.0 Premium, Sport, SMG, Maldives Blue