I would say if you are buying the extended warranty, wait until near end if your factory warranty. Of course buying, say, a 7 year warranty is cheaper at beginning, but that is because factory warranty covers almost everything. So the 7 years is really just 4 years post FW. If you wait and buy at end of FW period, your 7 year EW will go to year 10 of the truck. More expensive? Probably, but if you anticipate using the EW you will get more value later in a truck's life, it would seem.
Not true with the Mopar extender service contracts - if the truck was bought new or a certified pre-own, the extended service agreement starts at 0 miles/purchase date no matter when it was bought.
So yes a 7 year is only adding 4 yrs of most coverage - but the mileage component can be a big factor if you put a lot of miles on a year.
For used trucks (at least it used to be) the miles start at the purchase miles and date.
Q: When does coverage under my Mopar Vehicle Protection Plan, a product of FCA US LLC, begin and when does my used vehicle require an inspection before buying an Mopar service warranty?
A: New Mopar Vehicle Protection Plan coverage start at the ORIGINAL IN-SERVICE DATE OF THE VEHICLE (the date the vehicle was delivered to its original owner) and AT ZERO MILES, not upon expiration of the New Vehicle Limited Warranty.
Traditional coverage of Used begin on the CONTRACT DATE and CURRENT MILEAGE when you purchase the plan. Vehicles over 36 Months/36,000 Miles require a Mopar Service Contract to be in place on the vehicle or a completed vehicle inspection with any required repairs performed by an authorized Chrysler, Dodge, Ram, Jeep, Fiat or Alfa Romeo dealer or service center prior to purchasing a Mopar Vehicle Protection Plan.