Many threads on the subject - though not sure I've seen a specific solution for the Sprinter.
Opinions vary - so do what you are comfortable with. One you may not have thought of - some carry just the tire (no wheel) which is much lighter... and have roadside assistance mount it if needed. A middle ground that you may be able to find a way to store on board.
From what I have seen reported, the cost for a tire from a roadside assistance is very close to what you would pay on your own - though availability may be a concern based on where you might be traveling.
Not yet retired...
Florida (Michigan transplant)
2014 Hurricane 32A
2000 Infinity (previous)